I don't really understand how that helps. An example: Today 1 BTC is worth 10 of a stablecoin tied to the USD. I want to transact, so I trade for 10 of this coin and spend it. In three weeks, 1 BTC is now worth 20 of that coin. I regret transacting.

If you think your currency might be worth a lot more if you just hold on to it, you don't want to spend it for FOMO. Stablecoins don't change that.