In a completely free market, corporations are free to distort economic and labour policy so that poor unemployed people are desperate to get any job they can, regardless of how poorly it pays.
To add to this: if workers are underpaid relative to the cost of living in their area, they'll likely end up on some government assistance program.
Effectively, Walmart/Uber/etc get to double-dip -- they pay their employees less than a living wage, and based on the US tax structure, don't have to pay for the government assistance programs that their employees end up needing to make ends meet.
> To add to this: if workers are underpaid relative to the cost of living in their area, they'll likely end up on some government assistance program.
But that was already the situation before Uber came to the market? For all we know, driving Uber might have moved some of the people less dependent on the government assistance programs.
The Wikipedia article on minimum wage laws [0] has a pretty good overview of some of the most common arguments for and against. Really, though, the whole article is pretty interesting for a Wikipedia piece and illustrates the level of disagreement between economists over the effects these laws actually have.
Some jobs are viable at $8 /hr but not $15 /hr so the business have to eliminate positions to stay solvent. That means someone who could have taken the lower paying job now has no job at all.
Also, inflation. When everyone is making at least $15 /hr then that $15 means less than it used to. All costs of goods go up to match the new supply of "wealth". Burger flippers make $15 /hr but burgers now cost $10.
In more meta terms: manipulating the market is never easy if it's possible to do successfully at all.
My opinion is that having a minimum wage influences people to not make their own target, since an authority figure essentially deemed one hour of work is worth X dollars. Removing the minimum wage would make workers think for themselves how much they should earn and I believe that inclusion in their earning process would lead them to plan better, work better, and therefore earn more.
Essentially, I believe that when the government thinks for the people like declaring a minimum wage the people tend to avoid thinking about it themselves.
This is why minimum wage and other laws exist.
See also: race to the bottom.