I guess it is pretty new. Looks like Uber launched the, "moto," option in April in several cities, mostly in SE/Southern Asia.
Here's a piece I found on it in Vietnam:
https://newsroom.uber.com/vietnam/ubermoto-eng/
It worked the same as any other Uber, you select, "Uber Moto," instead of, "UberX," or, "Uber Black." (those were the only options in Ho Chi Minh City)
I did see a few surges on UberX, but never on Moto. So there's that too. But even at 2x an UberX would be maybe $5 for most places town. As I said above, in a car, you're really subject to horrible traffic. A motorcycle can take smaller streets, cut around cars, etc. It was never really scary for me though.