It's sort of the default state of assumption about the world in my opinion. "Everyone is an idiot except me" makes the world incredibly simple - frustrating, but simple. "Other people are incredibly bright and talented" is a scarier thought at a first look, plus it's vastly more complex because then the second question: "Why are there still problems in the world" arises instantly.
Personally I think it's wildly comforting and explanatory to assume other people (typically) know better than I do. Means I can focus on my little corner of the world and I don't need to tear it all down and rebuild it. Design, fashion, modern art; there are loads of domains engineers tend to assume are full of idiots - and yet we don't seem to dominate them like you'd assume we would if they were, indeed, full of idiots.