Well, many people will go crazy over anything for no rational
reason; it's not just buses - there's fictional characters, the
military, cars, etc.. Same for me - if you ask why I like buses, I
don't know how to really answer you, because in part my liking of
buses is irrational.
Maybe it's because of the variety of buses out there (which I find
fascinating), combined with exposure since young (I have been using
buses since a child, and even before I became a full-fledged bus
user (my father once had a car of our own), I have been making note
of them - maybe they stand out because of their larger size. I
have, since young, wanted to take every single possible bus model
out there (which I almost acheived - I never got the chance to take
SBS 81S, the Leyland Lynx, SBS' Nissans, and I still am unable to
get on board TIB 838H, TIB 905Y, TIB 1024H, and TIB 890E) to
experience what it's like to ride on one of those models.