I'll only talk about healthcare here, because this could degenerate into a flamewar otherwise, and I want to avoid that. Also, I'm no expert on politics, economics, or healthcare, so I'm open to any corrections. I'll try to remain as neutral as possible.

People have different thoughts about economic policy with regards to healthcare. Additionally, there are some cultural concerns.

For one, conservatives feel that liberals are too idealistic and don't have a good plan for actually paying for socialized healthcare. This is most commonly used against Bernie Sanders. Liberals argue that "competition drives down cost" is equally, if not more, idealistic.

Second, in places with "socialized" healthcare, health is thought of as society's responsibility, not the individual's responsibility. This conflicts with the American notion of individuality. Conservatives argue that the US's culture makes socialized healthcare infeasible without costs ballooning out of control, because people are selfish and don't care to protect their health. There is plenty of debate on this matter.

I'm guessing that healthcare is not the most important reason that conservatives vote Republican. Although it seems like a huge issue, there are other issues that might make someone choose one side over the other, even if they disagree with their side's healthcare policy.