It's not that we like it, it's just that most other solutions are so complex and difficult to maintain that repetition is really not that bad a thing.
I was however impressed with FastAPI, a python framework which brought together API implementation, data types and generating swagger specs in a very nice package. I still had to take care of integration tests by myself, but with pytest that's easy.
So there are some solutions that help avoid schema duplication.
fastapi + sqlmodel does remove many layers that is true, but you still have other services requiring lots of boilerplate