Best for who? It's better for riders if rates stay unsustainably low and they can get discounted rides at the expense of VCs.

"better for riders if rates stay unsustainably low"

Rates that are unsustainably low cannot be sustained, by definition.

Not without outside pressure, which in this case exists. I've been using Uber for 5 years.

Exceptionally low rates means the cars that are picking people up are not the quality of cars people want to be riding in, nor the quality of drivers they want to be riding with.

You're conflating two things - the low rate paid by the riders and the rate paid to the drivers.

As long as the drivers are getting paid well, whether it be from fares paid by riders or by VC subsidies, it will attract "quality" cars and drivers.

A separate issue is the sustainability of subsidizing driver wages from VCs by keeping rider fares artificially low.

Best for people who want these new services to continue.

It doesn't really matter whether they continue as long as something else takes their place afterwards.