Could you please elaborate? I don't exactly follow. Nobody is forcing them to work for Uber. If what you mean is they have bills to pay, etc, it's not like Uber can just magically decide to pay $9/hr, they will likely need to cut most of the jobs at that point anyway.
If people are not earning a living wage, societies can either let them die in the street or subsidize them. Most societies will choose the later, because they're made of humans and not monsters.
That means that there really is a minimum wage, but it's paid in part or in full by the society. Companies that pay less than a living wage exploit the "humans don't like watching children starve to death" vulnerability and effectively steal from society. Additionally, paying a lower wage lets them offer a lower price to consumers which can drive out companies that were paying their customers an actual wage.
It's entirely possible that providing a "living" wage to a food delivery person just isn't worth it for consumers so they would rather just go get it themselves.
The conundrum is creating a system where there enough incentive is created to do the work no one wants, but at the same time distribute resources so that everyone is provided some definition of "standard of living". This is difficult when the value of (most) human's work is ever decreasing.