Musicians are paid to record music. If they were not, as is the case for ai data, we would indeed consider it theft.
I remember reading literature from the 1930s, and there were quite a few folks who thought that the musicians-doing-recordings were stealing from the old-timers who played for live audiences.
History does not exactly repeat itself, but it rhymes
Going back to the previous example, say I pay a different coworker $50 for the data to train the chimpanzee and then use it to replace the first person. In either case they lost their jobs while receiving nothing for it. In either case, what happened to them is the same, so how would they be stolen from in one case and not in another?
There is broad evidence that labs have used substantial amounts of pirated data, no need to reach for a new definition of theft.