No, UASF is for everything now. Miners don't get to make the decisions.
UASF's are to persuade miners to make decisions -- they're the gun pointed in their face (or in the case of BIP-110, the gun pointed at a lamp they might sort of like and would take 2-3 days for a replacement to arrive).
The only environment in which you wouldn't need miners would be one where proof of work didn't matter.
The only environment in which you wouldn't need miners would be one where proof of work didn't matter.