They combine one strength of sovereign currencies (stable unit of account and store of value) with some strengths of cryptocurrencies, chiefly self-custody. If

They combine one strength of sovereign currencies (stable unit of account and store of value) with some strengths of cryptocurrencies, chiefly self-custody. If someone is invested in e.g. Bitcoin and thinks they can sell the peak, turning it into $stablecoin is the easiest way, and the only compelling reason to then move that value into sovereign currencies is: you want to spend it, or there's reason to hedge on the stability of the peg. If you're planning to re-enter the market later, (actually stable) stablecoins are just as good, and are what a lot of these traders will have when they sell, so why do two additional transactions, even if they don't trigger taxable events, which they would. I don't own stablecoins.