I think part is location, and the other part is fear that parents have for their kids.
I don't think going by car is necessary bad. I used to hit up my neighborhood, and then after I begged for 1 hour, my dad would take me out to other neighborhoods. Since he didn't know the area, he'd slowly follow me while I was going door to door. In some areas, it was clear only ONE house actually was doing anything, so that would be a clear drop off and then back to "pile" in the car
God damn I missing trick or treating. If I ever have kids, which I hope doesn't happen at this stage in life

, I'm totally going to let them dress up and have fun, put out some halloween decorations, and have fun passing out candy. Probably have them join a bigger group of kids supervised by a responsible adult (one that knows you don't need to literally have GPS collars...you just need to keep track of where they are, and look for any assholes in the area that might cause trouble)