Because many of their 'leaders' sold out a long time ago,

and the Evil Party made it worth it to them.
Here's part of it, the whole thing with an illustration is here.
This is hysterical, check this out. After getting caught plagiarizing and lying about a bunch of things in 1987, Biden dropped out of the Presidential race. He was asked about claims he made about being an activist for civil rights and he came clean, admitting that none of it was true.

Years later he resurrected the lie and in 2012, while speaking to the NAACP, Biden claimed that he would go to "Reverend Wright's" church before heading out to desegregate movie theaters.

In 2014 Biden replaced Wright with Reverends Moyer and Holloway. Both Reverends were asked about Biden, neither remembered Biden ever coming to their church.