I know about drug dealers using instagram or telegram but using cex makes even less sense in this line of work lol. In a dealers position I'd rather opt for decentralisation and security when off ramping than using surveillance infrastructure only because its widely adopted I guess...
In my own line of work I often accomodate clients paying in other crypto by using a swap service so I can keep the benefits of staying in monero, even though it has only the liquidity of a privacy freaks network 🙂