That's because Blue ain't the champ in those games. The games in which he was a champ he had a rather poor personality.
That said, while Blue slightly mellows out in the sequels, he's still pissy over him being beaten by Red "I was once the CHAMPION, although it was only for a short time... That meddling RED did me in...", and he still ain't all that humble, either, "... You're telling me you conquered all the GYMS in JOHTO? Heh! JOHTO's GYMS must be pretty pathetic then."
Blue's sister also comments on how Blue constantly not being 'round causes trainers problems. He doesn't care whatsoever 'bout his position as gym leader, it would seem. --- "God is great, beer is good, and people are crazy" "I don't give a damn what other people think. What do ya think about that?"