Never said they shouldn't, just said when it's the exact thing someone else created that someone else uses withoutIf you add music to a YouTube video, whether you’re earning money on said video or not, you better have permission to use it. If for no other reason than YouTube will copyright flag your video. I think the cutoff for usage is 30 seconds IIRC, my wife is the expert on that as she runs our channel.
But it’s not just music you add, it can be background music...playing in a store for instance...and they can flag you for that. They take this stuff seriously because people want to be paid for their work/property. And I see no issue with that.
consent, that's the pivot.
Now, I don't copyright music, nor have I truly used someone else's musical property without consent for my own profit..... I just use the theory/idea that music can't really be brand new/never thought of before....
Just the instruments, is all.