"Who would benefit from that?"
Those who need IPs that are owned by people who have no uses for them and just hoarded them when the internet was just an experiment, moreover often built with taxpayers money, and while being often paid with taxpayers money? The initial allocation of IPv4 wasn't fair at all. Not even clever.
Making them non routable until their owner abide to the same actual rules to which everybody else have to abide too would be fair. Why they should be exempt?
In the centuries many hoarded resources until they had to release them because it wasn't legal any longer. This is a kind of internet "latifundium" - quite idiotic, especially from people who usually think about themselves as "liberals" - but "hey, don't touch my big /8, serf!"