I think Three-Eyed Crow hit the nail on the head.
The moment your p2p Mu* starts making money, and is using either an intellectual property OR dice system that are not open source, you open your game up to all kinds of trouble ranging from actionable cease-and-desist letters to lawsuits. If the IP owners allow a p2p game to exist, it could set a legal precedent that would remove their protections if someone decided to make an MMORPG using their IP. They MUST act or risk losing protection of their IP.
Having said that, I also think about the number of Mu* I've been on and some of the self-obsessed, batshit crazy staff I have met. Sure, I'm sure Mal and Inara from SerenityMush seemed okay at first...and then months later I was getting calls from Mal begging me to login and entertain his RL wife.
I wouldn't trust 60-70% of any musher I've come across with my personal phone number let alone to believe that any money I paid for a mush would be used they way they promised. People are needy and greedy and the Mu* community is loaded with people who are at-home shut ins with warped concepts of the way actual humans communicate with each other. Rational, mature adults are in the minority. So would I roll the dice to pay for a Mu* only to find the owner of the Mu* was using the cash to cover his rent so he could stay home all day and harass women for TS? Fuck no.