[WithinReason]

I would use UTC of course. Why would you do anything else?

[Dylan16807]

Then I don't understand what point you were making when you said "UTC is effectively a timezone."

But if it was notably more convenient, I would expect to see more people using it right now, even when it's not the default.

[WithinReason]

It's a matter of compatibility, e.g. you're not going to start measuring length in meters when everyone else in your country is using feet. That's why I said UTC is a time zone, nobody uses it outside of the UTC time zone, therefore nobody uses it outside of the UTC time zone.