I won't disagree, however, at the end, Spidey was finally an official Avenger. And years before it was so comercially exploited in Bendis' New Avengers. I have to say, I do think the traditional reasons for Spidey not being made an Avenger make sense for me (creatively, the hard luck hero cannot be a part of Marvel's most prestigious team of super-heroes. It ruins the character), however, this opened a door for him to occasionally join the team, because there is no real in-story reason for which he shouldn't do so (he's friends with most of the Avengers, and has assisted them in countless occasions).
Peace