All excellent points, Arthur.

Also, regarding "The CEO of Betterment said they’d employ 1 advisor for 10,000 clients."....

I wonder how genuine that statement/forecast really is, considering Betterment is marketing a wrap program to independent financial advisers through Betterment Institutional. Not that their platform can't handle it, I'm sure it can once the client is acquired. But they're using traditional advisers to acquire those new clients and manage those relationships. They're obviously not counting them in their 1:10,000 ratio.

https://www.bettermentinstitutional.com/

This suggests robo-advisers have marketing limitations, and that's where even offering a "zero fee" won't be able to help them. Investors need people, and people cost money.