I do not see any use in stable coins, besides keeping the money on exchanges while searching for a market entry point. Besides, the most stable coins are regulated and are backed only by a certain percentage and not in full amount.
Besides that function, stable coins are also suitable for online payment instruments. At present we see a lot of shops that provide payment through crypto currencies that don't have a stable value, of course it has an impact if the network is slow. Prices change quickly but transaction speeds cannot match that.
the use of stable coins I think can also be used in online stores, purchasing goods with stable crypto is better in my opinion. as you said that when using a coin which stability is less profitable, people will think twice about making payments with it plus a large fee when using btc payments
It's probably the regulation that makes that impossible considering that the funds to back up all these stablecoins are issued by the government so the government could lay hand to any stable coin company although I dont really sure. The stability of a stablecoin is indeed something most suitable to be used for the means of payment method but until today I can't see the adoption anywhere else maybe there's some reason behind this since the adoption of a stablecoin should be no brainer because it is practical.