The hatred for politicians who change their views baffles me

There are a lot of people who will hate a politician that changes their views according to what the people want. They'll say that these politicians are phony and are only changing their views to get votes. That's what they're supposed to do. Why the fuck would we not want politicians to change their views according to what we want? How is that bad in any way at all?

For example, let's say that the people really wanted prostitution to be legal, so we get a politician whose morals tell him that prostitution should stay illegal, but he promises the voters that he will make it legal if they vote for him, so he wins the election, and he makes prostitution legal. Why the fuck does it matter that he didn't want legalized prostitution when he still did it anyways just to make the people happy?

If politicians do whatever the people want them to regardless of whether or not they like what the people want, then they get votes. We offer incentive with our votes for politicians to do what we want.