Unethical because guess what people who drive for Uber probably care a lot about losing $115 and will work their ass off: i.e. drive fatigued, perhaps kill someone ... to make sure they don't.
I have noticed that drivers of car sharing schemes (where you pay per minute) are a bit eratic at times though. I’m not sure if that’s because they are inexperienced drivers, or just the mentality of “I need to rush, this is costing me money!”.
edit: Googling turned up that this seems to be a thing in at least San Francisco, London, Dublin, Wellington (NZ), Sydney, and a few smaller UK cities.
I always thought, if you are rich don't bother with a car & chauffeur just get a taxi everywhere, and get their faster.