But there is varying degrees of trust required. Also the quality of trust.
Where's the trust in a bitcoin tx?
You have to trust that the restaurant where you're having lunch will accept BTC as payment. In reality, using Bitcoin requires the same trust-based infrastructure as everything else because the only way to buy anything with it is to trade it for fiat.
That Bitcoins still have a value when you sell them
Well, not really. Tainted coins is a real, growing problem that BTC hasn't solved yet.
In short, BTC is not fungible.
sure, and 1 UST = 1 UST, but it turns out that people who thought they didn't need to trust the asset held its value are considerably poorer than they were before.