> A more convincing rationale [...] keep income that would otherwise have gone on drivers’ wages.

My pet-theory is that the growth of these investments comes from demographic timing, where (esp. circa 2015) investors were excited by the idea that aging baby-boomers would create a uniquely rich field of customers with disposable income but unable to drive themselves.

If so, then "eliminating drivers to save wages" wasn't the original intent, but it may be a way to continue to drum up investment dollars if it looks like that demographic window will close before the technology is ready.