With fiat, I at least have some idea who I am trusting, and if my trust is betrayed, I have some idea who to work with others to organize to work to inflict punishment. And, the people involved are aware of that.
With crypto, I have to trust an anonymous network of people that I have only distant and indirect indications aren't, in overwhelming majority, mutually cooperating agents of a single potentially adverse party, and no idea of who to go after if my trust is betrayed. And the people involved know that, too.
Yes, except the trust is free. Bitcoin replaces that trust with burning electricity.
It's kind of like standing on the ground. The surface of the Earth stops you from accelerating under gravity for free. But if you want to hover just above it, you have to burn ungodly amounts of energy, because you're now replacing surface with active propulsion. This is the same relationship as Bitcoin has with trust.
And yes, flying is occasionally useful. So are trustless systems. But both the ground and trust are features that cut out a lot of unnecessary energy usage from our lives.
With a blockchain, you still need to trust the counterparty, but now you also need to trust that the coders have properly designed and programmed the system, and that the miners either don't have the power to corrupt the system or aren't corrupt, and you need to trust whatever exchange you use to get into and out of the cryptocurrency.
Plus, you've added in a significant amount of time--at a minimum 20x the time with Bitcoin and significant transaction fees that as a practical matter have exceeded card interchange fees by 2x or more for the past 3 years straight.
Your right about their being more variables...with cryptocurrency.
One obvious tradeoff you're not considering is that of a criminal getting its assets frozen, for instance. There are less black and white situations where you might prefer bitcoin as well, if you have a little imagination. If you could address that, I'd probably appreciate your comments more.
I am emphatically not taking a stance on which I prefer here, I might add, just pointing out that there are more variables here than you're acknowledging.