Things are still priced in dollars though with btc acting as the medium of exchange.
You see a pupusa for $2. You type $2 into your wallet which converts it to btc based on the current exchange rate. The recipient receives that btc and ideally converts it back to USD immediately. Both ends of the transaction are valuing things in dollars but uses btc (perhaps over Lightning network) to transfer the value. In this scenario, there is little to no exposure to the volatility of the price of btc.
Western Union is the only option for so many people around the world still. There definitely seems to be a need to disrupt cross border remittances.
This link says that it's considered "legal tender" in El Salvador: https://en.wikipedia.org/wiki/Bitcoin_in_El_Salvador