The IRS deduction rate per mile plus minimum wage per hour. Anything below that is so low that it is immoral (and would be illegal in any civilized country).

It'd be illegal in this country if not for some very creative stepping around the issue on the part of the "gig economy". (Which may itself be illegal but it appears Uber has become to large for this to matter)

Its a voluntary agreement between two parties - they should be able to make whatever deal they want as long as both parties are amenable. If not amenable, go elsewhere.

They don't agree voulnatrily on that low payoiut per mile because Uber and indivudual drivers have very different bargaining power. A free market can only exist between well-informed rational actors that can both walk away from the deal. In the face of huge power disparities you need limits on the power of the stronger player for a long term market to exist. This is exactly what minimum wage is. So don't trode out the tried old propaganda of cut-throat capitalists such as "they took the deal".

The comment I was replying to said they would optimize for paying them “as much as possible”, not minimum wage.