These authors are either making the same assumption (that the reader will have seen every cultural reference they have), or are specifically writing only to an audience that fits those specs, and don't care about anyone else.

To use a cultural reference, that's one of the things that turned me off about Gilmore Girls. Lorelai and Rory were such a snotty little clique in themselves, positively broadcasting the attitude that if you didn't catch every single one of their references, you simply weren't cool like them.