So I ventured into indie music production during lockdown and here's the thing -- covers are a notoriously vague area when it comes to copyright and licensing. It is easy and cheap ($10-15) to get a cover license. You are required to give out royalties. Most covers published on YouTube just end up losing monetization.

But, and here is where it gets weird, what defines cover is extremely limiting. For covers, the song must follow the exact general tone and pattern of the original. Anything else is considered derivative work and an infringement, even if the license was bought. So if a guitarist adds a simple vocal explaining how he played it -- it is not a cover. It's infringement.

Also, under DMCA, covers are not fair use. I also expect lesser music companies letting YouTube videos slide as we now have YT Music and these covers directly compete with the original. So they might just not be comfortable with getting your money, they also don't want a cover beating the original in playlists and charts.