If someone is willing to work for $5/hour, I can't pay them $5/hour, even if that's all I can afford. Not all jobs should have to pay a basic living wage for two reasons. Not all jobs create enough wealth to justify that wage, and there are lots of people looking for side work, or just a bit of extra cash, and aren't relying upon this type of job for their living.

A 12 year old running a paper delivery route on their bike doesn't need $15/hour and isn't creating $15/hour in wealth, yet the kid and the employer would be happy to agree on some lesser amount.