One advantage of stablecoins is price stability. Merchants don't have to worry about price volatility when transacting in stablecoins. In the past and present, there have been a handful of projects proposing issuing altcoins (non-stablecoins) that will lead the future of crypto payment. What's the fate of such projects, will there ever be considered viable?
for payment purpose stable-coins are better option, since their value is changing a little and you could not use volatile coins for merchants purpose, due to changes in price that can ruin your profit