This question was inspired by the thread “in to” vs. “into”
It drives me crazy when I hear something like, “I was waiting on so-and-so to get back to me about my question.”
To me, this is a clear example where one should use “waiting for”. The phrase “waiting on” refers specifically to the sort of thing done by waiters and waitresses. It is an act of service, to stand by someone, and wait for their instructions.
A lieutenant might wait on a general while the general decides what to do next. But one does not wait on an Amazon driver who has the thing he ordered; he waits for the Amazon driver.
I do realize that many people feel differently than me on this, so I’m not going to accuse that usage of being wrong. But maybe it is more common among some groups than others? Might it be a geographic thing and age thing?