on routine traffic stops. Insty says
If you consent to a search, however, all bets are off. It’s hard to see why anyone would do so: If you’re a criminal, you’ve got something to hide; and if you’re not a criminal, why would you want to let the police paw through your email?
True enough; the reason people do is they're pressured into it. People, including lots of honest people, are somewhat scared of the cops: they know they can be arrested for pretty much anything if it's a bad one stopping you. They may have the kids in the car, be on the way to a job, may just be short of time and they get
"You realize refusing permission looks suspicious?"
"Sir/Ma'am, I can keep you here until I can get a drug dog to sniff around the car..."
and so on. Someone short of time or intimidated gives in and says "Ok, search." Lots of cops are very good at pressuring and scaring people into giving permission. That's why so many people surrender their 4th Amendment rights to the man with the badge.
And yes, they can make you sit around for a while waiting or a dog, and there's no set time; I asked a lawyer about this once and he said the time 'depends on the circumstances'. Think about that while wondering why people get spooked and surrender.