$15 an hour is not a livable wage unless you have at least somebody else also working. Moreover, moving costs money and involves risk that some people because of personality or circumstance cannot afford to take that risk. Do you expect employers paying $18 or $20 an hour to cover the cost of moving expenses?
FWIW, since I try to not be a hypocrite (I try), I pay people working hourly for me at least $20 but oftentimes, way, way more than that (I'm a real estate broker so I occasionally need people to drop everything and knock out a punch list so we can go to close).