Why so many people use "house rules" in EDH/Commander?
Generally speaking, in any game community the casual players are going to have a different attitude toward banning than the tournament players. In the case of M:tG, the tournament formats are very fine-tuned and the most hardcore players tend to play in sanctioned tournaments, so if anyone's going to be banning cards that aren't officially banned, it's going to be casuals who don't like losing to certain stuff.

EDH is and has always been a very casual format. It's an open secret even among the people who designed and govern it that the format would be broken in a lot of ways if anyone tried to "solve" it. Drew Levin said that "Commander is a format where everyone puts Sol Ring in their deck and then apologizes if they get to cast it". Even "serious" Commander strategy articles will often trail into digressions about not breaking the format too hard.

All of this is to say that if casual groups are banning a card, the thought process is probably something like "ok, we get it, you can beat us with that card. We'd like to actually play a game this time." If that bothers you, play a "real" format. I had to play Commander all of twice to decide it wasn't for me.

EDIT: I originally attributed the Drew Levin quote to Aaron Forsythe. I did find another article about an EDH deck created by Forsythe; the comments thread is pretty pertinent here.