I don’t understand the significance you try to cast on your closing statement —it’s trivial. If you sell something away, you will have to pay for it if you change your mind and want it back. That applies not just to music rights but EVERYTHING. You can’t sell a car and then pop up on the buyer’s door next Saturday asking to borrow the car for an hour or so.
Nobody lose their rights by accident, it’s more like lack of vision — be it blinded by a lump of money or just plain negligence. People WANT TO sell their rights to (not) their music, and that’s completely their own problem should it backfire.