The point is that it encourages centralisation, and where mining is centralised, miners can play games like blacklisting wallets if they want to. Particularly if, say, most of the mining capacity ends up somewhere with an authoritarian government that might take an interest.

(I am willing to admit here I don't know enough about monero in particular to grok whether the mining blacklist thing would work on that chain. I'm pretty sure it could for BTC)