I stopped for two basic reasons, but could have been a third.
First, cross-over disease. Marvel and, apparently, DC (I didn't collect DC much) got in the habit of developing special "short series" where characters crossed over into other books or new mini-series were developed. This, was of course, to maximize sales, but it maximized my frustration. I was reminded of this today by a tweet (h/t to Jacob Levy) that pointed out a fun cracked article that highlighted a key X-Men issue (Wolvie gets Colossus good and drunk and then beaten up) that was a result of one of these series:
It has its roots in Secret Wars, and while most people remember that as the crossover where Spider-Man got a new costume that wanted to fuck him so bad, it became the most popular villain of the '90s, that was far from the only notable event. The whole idea was that there would be a big change for every book, so everyone reading Marvel Comics would have to pick up Secret Wars in order to find out what the hell was actually going on. This is basically the formula that modern superhero comics are built on, which makes it the most diabolical and successful supervillain plot of all time.Indeed. This led to a proliferation of comic books, which increased the $ spent, and I got tired of having to buy many books to follow one character.
Second, clone disease. I quit when Spider-man was apparently not the real Peter Parker. Ug. I hate clones, as they are almost always a dodging plot device that leads to bad stuff (no accident that Clones are mentioned in Star Wars but only rear their ugly heads in the prequels). I almost stopped reading the series of Star Wars books that took place after Return of the Jedi since clones were featured.
If I had stuck around for a while longer, I would have then quit due to re-boot pandemics. Yep, the editors let the writers of comic books write themselves into a box. When they realized that they were trapped, they re-booted the character or the entire series or the entire universe. Why should I care about anything in this universe if it can be re-set any time they feel like. Well, a new universe with the old characters re-set means that I have nothing at stake anymore so good-bye.
This, of course, also occurs with the movies: two sets of Spidey's, three sets of Batman (if we include Adam West's version), three sets of Superman with the new one in a few weeks, three sets of Hulks (including the Avengers' version which is, thankfully, superior), and so on. Much of this is driven by the need to keep the rights to the character (Spidey), but it diminishes the value.... unless they do it really, really well. I was not happy with a new Spidey series, but Emma Stone and, oh yeah, Andrew Garfield made it work. The new Superman is probably better than the most recent one, but will still probably fall short of Christopher Reeve's. Then again, I watched all three Superman non-animated TV series (the original, Lois and Clark, Smallville). Well, the second one had a lot more to do with Teri Hatcher, but anyway.
I guess I tolerate the TV/movie reboots because there is a chance that the new version is as good or better than the old. My completely half-assed take on comic books is that never happens. More importantly, if you follow a comic book, you have years and years and dozens and dozens of issues invested, so a new version rips out all that investment. I hate that. Do you?