Stablecoins are a UX gain for most people around the world. It allows people to create technologies that feel familiar, akin to saying you're paying with USD+, a Peso+ or a Euro+. This creates less resistance to using foreign or unfamiliar technologies like Bitcoin or any other blockchain based currency. Stablecoins also allow for industrialization. It's a translation technology that doesn't focus on "price of asset/line goes up" thinking and instead focuses squarely on transactions, payments and banking.