You don't want to create a commit in the parent repo all the time. If you fix a typo in a comment in a submodule, why commit anything to parent? Anyways, which parent, since there can be many. There should be more than one. Otherwise why use a submodule?
Another problem is that one forgets to update submodules when switching branches. Afaik git does not do this because of possible data loss in submodules?
I like submodules in general. They are great for dependencies where you want to follow more closely than release version. Still, it would be even easier in a monorepo. The main reason is probably that every anti-dependency is visible.
