I get what you're saying but I used to live in Illinois so I have to defend them a little.
First of all, all the guys I knew there were rabid Illini fans. Based on that sample I can say Illini fans stick with their teams through think and thin, which is saying something since there's a lot of thin.
My friends were deeply scarred by what they consider a bad call at the end of an NCAA tournament with us in 1984. I don't remember the details of that call. They spoke of it fairly often not because they knew I was from Kentucky, but because they can't let it go.
Also lets not forget they were a 3 seed and made it to the elite eight last year. They got beat by UConn. They've had some pretty good teams with decent seeds. In the last 4 years 3, 4, 9, 1. They're not a historic blue blood but they haven't been trash at least lately.