Ser, you're not trying to understand the point being made, nor are you getting the context. Centralized mixers/services are incentivized to be HONEST because if they're not, then users will go and use the next tumbler = profit down. Plus it's developing to be a very competitive business like VPNs, and it will be a competition on who has the lowest fees, who has the best UI/UX, and who simply does the mixing/tumbling most effectively.
No, I understood your point and your context, I simply disproved it with economics: Mixing sites are incentivized to be dishonest since they can profit from selling your data even after they cease operations. Furthermore, there's no way for customers to verify that their data hasn't been sold, so a dishonest mixing site that sells data will be able to undercut the fees of an honest mixing site that does not sell data.