1. Low synergy between films and comics. Popular capes films would have been the perfect gateway to comics if the comics resembled them in any meaningful way.
2. History. The best starting point to a manga is chapter 1. Unless it's a direct sequel or spinoff, you won't be expected to read anything else for additional context to the story and setting. Capeshit has a canon that requires years of reading all sorts of shit you might have no interest in just to catch up to modern releases.
3. Creators. Manga is written by one author for the entire run. At no point in the run will the author be replaced by someone else. At no point will the artist be replaced by someone else. That's guaranteed. Capeshit replaces authors and artists like they're the least-important part of the product, when they're the most important.