If its so good why do very people use it?
Because it is not a cheap aircraft to operate - that is the big problem with getting a decent training aircraft and why most Schools use the aircraft they do instead of the best for the job. There have been many threads on which is the best training aircraft for schools and I think on all of them the C152 comes top for exactly this reason, though many instructors would much prefer other aircraft.
(And why do so many PILOTS get my name wrong - do they not know their classic aircraft types or can they just not read?)