May I play the devil's advocate? :P

http://en.wikipedia.org/wiki/Design_by_committee

Seriously though, it's impossible to incorporate everybody's opinion, especially since everyone is a self-proclaimed expert on user interface, and very hard to filter what is best and still keep consistency. Thus I understand those developers who shut all input off.

User facing decisions on a project worked by a team (or procured by a customer) require more than just good taste and usability understanding. It needs social skills and a way to explain what's on your mind with clear words and arguments. And that's not something you can always do. Sometimes I feel like a painter who is being asked why is that brushstroke there.