Because they can, they pay no price for it
That's what happens when you have monopolies and politicians who are supposed to antitrust them are corrupted by them
we have AI algorithms that can parse millions of youtube comments daily for "hate speech" but can't figure out if someone is using their domain for a year?
then maybe it should be forbidden to renew domain if you haven't use it for a year instead of increasing prices for everyone, how convenient for domain registrars