I’ve worked with gameplay programmers who can’t do simple 3D math, c++ programmers who fundamentally don’t understand pointers, backend developers who didn’t understand globals were shared state and cause race conditions, etc.
It’s not that SQL is hard, it’s that for any discipline the vast majority of people don’t have a solid grasp of the tools they’re using. Ask most tradespeople about the underlying thing they’re working with and you’ll have the same problem.
Im more surprised by software engineers who do know these things than by the ones who don’t.