Reducing other’s freedoms because they’re bad for you is something I’d consider evil. People should be allowed to make choices for themselves. If you think they’re harmful than you should try to educate people, but you shouldn’t try to make them having a choice (which you were allowed to make) illegal.
I think people are dissuaded by a few factors.
The first is obviously it’s very difficult.
The second is you’re almost certainly going to be caught. All the resources in the country will be spent finding you.
Also, and I think this is potentially the most important, is the result isn’t worth it. It’s not a “cut off the head of the snake” situation. Trump isn’t the end of this. Hell, Vance might be even worse. If Trump is murdered he becomes a martyr. That’s not what you want to happen.
It’s not going to improve anything, so why throw your life away attempting to do something nearly impossible?
I think the only option for killing Trump that has a good outcome is someone in his cabinet or in a senior position in the military does it to stop him from doing something. Anything else probably strengthens his base.