Slightly off topic, but it's rather poor form to use the term slaves to refer to people who clearly aren't. Unless the driver had, say, taken out a loan from Uber in order to pay for their car, they don't even meet the mark for indentured servitude.

There are millions of actual slaves living on this planet, children and adults forced into labor, sex, what have you. Calling someone with a shitty job a slave devalues the meaning of the term and softens the reality that there are right now more people than the number you have ever met in your life and likely ever will who can be bought and sold as property.