[piecemeal]

Uber has enough market power that it's often a monopsony, and thus has the power to depress wages more than would happen in a market that didn't have the winner take all dynamics of most app-based businesses.

You can paint it as "natural" for a monopsony buyer to squeeze every possible penny for themselves, but most humans have an emotional reaction to interactions which are perceived as unfair. This isn't irrational or dumb. It's natural and it's part of being a human.