Yeah, but even with semver library owners have problems. If you need to make a critical change (e.g. a security update), you can either (a) wait until everyone does a version bump on their own schedule, or (b) do the version bump yourself, which means you're deploying every app that relies on your library. (a) might not be feasible for critical things, and (b) means that you might be deploying changes that the app isn't ready for yet.

For example, if master is v1.5.0, and I'm an app that uses v1.1.0, then if the library owner bumps to 1.5.1 for a critical update, I need to go from 1.1.0 -> 1.5.1, which might involve changes I'm not ready for yet. I better have phenomenal integration testing to make sure the update is safe to do.