You assume that there is some relationship between churn, and total unemployment. I don't see how that would work. If Uber were convinced that it was terribly

You assume that there is some relationship between churn, and total unemployment. I don't see how that would work. If Uber were convinced that it was terribly immoral to fire someone, they would just put greater effort into making sure they got the best people in the first place. So your policies favor a society with 5% of the people unemployed 100% of the time, instead of 100% of the people unemployed 5% of the time. Job security is of questionable social good because it places a nonsensical emphasis on the harm of getting fired, as opposed to the harm of not getting hired in the first place.