Frankly, Pyan, that's because with something like this, given the popularity of the films (and, consequently, the books, where people who wouldn't normally have read them are concerned), like so many secondary tomes, whether it be of scholarship or whatever, it has become necessary to explain terms such as this because fewer and fewer people really do know these terms (amazing as that may seem); so adding these is an attempt to bridge that gap -- sometimes successfully, often not; but necessary to avoid alienating a rather large percentage of their potential buyers -- a larger percentage than would find such a practice annoying, I'm afraid.....
