One part of the problem with this question is the same as a lot of other things: "Why do you ride a motorcycle?" or "Why drive a truck?" or "Why do you want something that'll drive that fast?" and so forth. Sometimes, depending on who you're answering, nothing you say will make sense to them. Which is also where you run into "People shouldn't be allowed to (fill in blank) bacause it's dangerous/not needed/not right/etc.". Here's some further thoughts on this.
Early on, it was doing what Dad and Grandpa did, they went shooting and hunting and it looked interesting. So Dad started me off with a .22 rifle and it went from there. It was something that I enjoyed, and what more reason did I need?
It was a while before the idea of use for self-defense really meant anything to me. It was some things that happened with Dad's work that brought that home. Dad spent a lot of years in the highway patrol, and I once heard him mention to mom about some jerk threatening him. That makes you think, what if jerk showed up at the house while Dad was away? That took the idea of defensive use out of the realm of something in a book or movie and brought it home. It was still not the foremost reason I liked guns, but it was there.
When I started shooting handguns, Dad taught me their use the way he had learned it as a state trooper, based on his seeing handguns as good for a: target shooting and b: self-defense, and if I needed one for b, I should know how to use it correctly. Which was also a lot of fun to practice.
It was about this time that I became aware that there were a bunch of people out there who didn't think I should be allowed to own or shoot guns. According to them guns weren't 'needed' or 'safe', and since criminals used them they should be either banned or severely restricted. Which brought to mind what I still think: if I'm an honest citazen and not violating the law in my use of them, it's nobody's damn business what I own or how many. Or, in light of some people trying to control that, how much ammunition I own. And if banning guns would take them away from criminals, how was it that laws about robbery or murder didn't keep those same dirtbags from committing those crimes? Which also helped lead me into distrust of politicians who wanted to control some part of my life. Or some more parts of my life.
Years later, I wound up married, then with kids, and between time and money had very little chance to shoot. Then, about the time I started taking the kids fishing, I found a place to shoot. That helped to do two things: made me take them out when old enough to learn to shoot, and got me back to shooting on a regular basis. And I've kept that up since.
All this leads up to my personal why I own guns. I like shooting for a variety of reasons, I like working on/with firearms, I like owning the means of self-defense if needed, and I like to hunt on occasion. And I really like the knowledge that it makes a lot of politicians nervous to know that a lot of the peasants are armed.
Happily, the chance of my needing to use a gun for self-defense is fairly low where I live, so with luck I'll go my life without having to do so. But having the means to do so is a very good thing. When someone tells me the police will take care of that, I wonder how? Are they going to be in the parking lot when I'm walking through it? Are they going to be in my home if someone breaks in? They can't be, which means that if it happens, I'm on my own. So are you. I believe that knowing something of hand-to-hand fighting is a good thing, but given a choice I will not depend solely on that; why should I? Why should I rely on a method that requires me to let a bad guy get within reach before I can act? Pepper spray? Please. It's better than nothing, but it's been shown over and over that someone who'd determined can hurt you badly or kill you before it can stop them. Guns should be left to 'trained professionals' like the police? We're back to 'will they be there when the trouble happens?' at best, and the unpleasant fact is that many law officers are flat lousy shots.
And there's another problem with the 'rely on the police' idea. As has been pointed out in several court cases, the police have no responsibility to protect you; their responsibility is to society as a whole. Which means that if they don't protect you, well, too bad, if you survive maybe better luck next time. Connected into this is the 'there are no barbarians at the gate' attitude gone over here. There are several costs and consequences to giving up all responsibility for your own safety to the 'authorities', whoever they are. The costs are highs.
As to those who, 'for the public good', want to take arms away from me, screw you. They break down into several groups.
Those who honestly believe that people should not be allowed to own arms of any kind, it's "not nice" or "not needed".
Those who think that if they pass another law, this one the criminals will obey.
Those who think the government should control large parts of our lives, and it does not serve the government for people to have arms.
Those who actually believe that only 'racists and bigots' own guns and those people should be controlled.
And those who do not trust themselves to own arms, and don't think anyone else can be trusted, either.
Nobody 'needs' to own a motorcycle, or a boat, or a lot of other things. And some of these people would like to see them banned, too. I've actually seen a proposal to ban the ownership of any knife, including kitchen knives, over a certain blade length, and unless you were a 'licensed' chef, they would have to have a button welded to the tip. This lady was dead serious and truly believed this was a good idea. But damned if I'll allow her belief to control what knives I own.
If the criminals would obey the law, they wouldn't be criminals, would they?
I don't want the government controlling any more of my life, they interfere too much already. And I'm not supposed to live according to what will 'serve' the government, dammit, and I will not. In many cases the reason many politicians want the ownership of arms banned is bacause they won't feel free to dictate to us how we'll live as long as people have a concrete way to fight it. Voting is one way, but in many areas voting districts have been gerrymandered so that an incumbent has little chance of losing an election, and in any case, the founders made it plain, one of the reasons for armed citazens was specifically so the government would know that people had, in a final extreme, the means to force government to listen- or else.
And for those who don't trust themselves or others to own arms, screw you. I don't depend on your permission to own arms, whether it be gun or knife or sword or bow, and I consider your lack of trust in yourself or others to be your own mental problem- not something to be used as a reason to act against others. Kevin over at Smallest Minority has had several cases of this type of thinking, and I am in awe- and some fear- of someone who sees an inanimate object as something that could 'corrode' their mental state. Only if you're squirrely to start with, guy. So LEAVE ME ALONE.
This has been a bit wordy and roundabout, but it boils down to this: I enjoy owning and using firearms. I enjoy working on them. I like having an effective means of defense if needed, and I really enjoy knowing that it makes some politicians nervous to know that people have arms.
I don't want a speedbike, but I wouldn't try to ban them. I don't want a car that'll do 150, or costs $100k to buy, but if you have the money and that's what you want, knock yourself out. I think many vegetarians- vegans especially- are nuts, but if you don't want to eat meat, it doesn't bother me. You don't like guns? THEN DON'T OWN ONE, and leave me alone.