I can sell coin at market or get a 1% premium all day long. It costs less than exchange fees. Buy orders don't move until I set -1% or better for the seller. Within the daily price fluctuations and worth it.

And yes, the fiat method is key, because you have to consider the implications to the seller. I can speak for the US only here. Nobody (that knows what they are doing) wants to sell using third party payment processors, now that the feds started surveiling them in 2022, with 1099 tax forms. That includes Strike, Cash app, Venmo, etc. In the US you can still use Zelle, for now, without extortion because it is a bank service and not considered third party.