There should be some system in place like you can only have X% of domains not being actively used for a legitimate purpose. And if you fall below, you will need to pick Y domains to relinquish or they will be randomly relinquished for you.
Also you have no way to properly define "legitimate".
I'm with you in spirit, but this is a hard problem to solve.
In principle I agree, but I don't really see how it can be solved in a practical way without a lot of collateral damage.