Oh, you mean like any regular job? Where you need to exceed everyone's expectations?
This is what a free market looks like. Don't like that? Take a look at Venezuela, and tell me you'd prefer to be dumpster diving for your next meal. Capitalism and Democracy are aweful aweful systems, but everything else is worse.
The difference is probably the level of expectations. In "any regular job" you don't get fired for having your ratings fall below 4.3 / 5 because a customer of yours had a bad day or fat-fingered 1 in a hurry.
The jobs with high turnover rates are usually known as "shitty jobs".
Do you really think that a highly competent organization that's hired hundreds of data scientists can't estimate/discount the base rate of fat fingered/random bad ratings?
(Fun fact: I don't know about Uber, but I know Ola does exactly this. They use "how would you handle this exact problem" as a warmup question on their interviews.)
It's good for them to keep drivers who committed (e.g. those who took Uber's help in getting a new car) on edge. It's not that they have shortage of candidates, or that they actually care about them.
