Why doesn't Gai use ninjutsu or genjutsu more often? According to the wiki, Gai is able to use ninjutsu and genjutsu, so why doesn't he use it?
I'd say because they aren't his strengths - clearly Taijutsu is so why should he use something that he isn't great at? 

It could also be that he has used them in the past and it, unfortunately, got him into some difficulty so he had to fall back on the tried and tested techniques of his Taijutsu :)