you don't pay tax on a used vehicle

That depends on the country.

That's right, I don't.

Good thing about cars and houses is that you can pay some amount officially and then pay more money under the table.

Right. But that is illegal and in my view also immoral. If you want to change the law campaign for it. But breaking tax laws is not a victimless crime. You are freeloading/stealing from the rest of us.

It's impossible to make people vote to give themselves less money.

That’s factually incorrect. Cf most of Northern Europe for the past 60 years.

Edit - ah, I think you mean politicians? My comment still stands though. I don’t know the polling in the US, but spending on social programmes in Europe is broadly inline with public opinion, so the insunuation of a democratic deficit is misplaced, at least here.