Not all people who are committed Dems are hardcore liberals. My step-daughter and her husband are loyal Dems, but about as socially conservative as you can get. My lib son-in-law is very religious (I am not, even though I consider myself a Christian) and gets upset when I make up (what I consider) funny lyrics to Christmas songs. He is also a Boy Scout leader, gun owner, and hunter.
My step-daughter, another committed Dem, is also very socially conservative. She's against pot legalization. She didn't like Bernie Sanders for president after finding out his tax plan would cost them many thousands of dollars. Btw, they're both doing very well financially.
They live conservatively and expect people to live traditional, moral lives. I'm sure there are millions of committed Dems who live similar lives.
So you're asking: why do they support and vote for Democrats?
That's a good question. I believe the s-in-law might eventually turn, but they both believe the Dem Party is on the side of justice, niceness, and goodness.
Republicans, however, are icky, greedy people who just don't care about anybody but themselves. Even though they know both the wife and I are Republicans. Actually I'm a conservative first, and Republican second.
But the wife and I overlook the snotty comments directed at Republicans by my step-daughter and s-in-law. They might turn eventually. Time will tell.