Agreed. At this point, they're hardly essential. I find them more irritating than anything. If something is that important, put it in the main part of the film.

Otherwise, I stay for three reasons:

1) Creative title sequences (I often wish these opened the film, as in the old days).

2) Amusing outtakes in comedies or the like (Pixar films for a while had some hilarious "outtakes" plus that hilarious performance of Put That Thing Back Where It Came From Or So Help Me on the end credits of Monsters Inc).

3) Music score. This is the best reason to stay through credits. Ever since seeing E.T. The Extra-Terrestrial during the original 1982 release, I have insisted on sitting through any credits that feature a score by John Williams.

Finally, here's one reason I won't sit through credits: Footage of the real person or people on whom the film is based. It has become such a cliche to do this. We get that it's based a true story, and don't need it underlined with dodgy home video footage that detracts from the glamourous sheen of what we've just watched. Stop treating us like dumb-arses with this incredibly passe trend and let the film stand on its own terms. Yes, it worked brilliantly in Schindler's List, but that was an important, almost unbearably moving part of the film itself (the credits came afterwards). Since then, everyone and their cat has copied Spielberg. Enough.

By the way, everyone stayed for the credits of Schindler's List, because 1) John Williams, and 2) The film was so powerful, the audience were rooted to their seats out of sheer respect (and shock). When the credits finished, the lights came up. I turned around (I always sit near the front) and saw no one had moved. Just a sea of tear-stained faces. Everyone remained in their seats for about another minute before getting up and leaving. It was one of the greatest cinemagoing experiences of my entire life.