Not all jobs are supposed to pay all your bills and mortgage. McDonalds and similar jobs are there for students and other people who want just part-time gigs paying some additional cash for their non-crucial expenses. Such jobs are supposed to be temporary, therefore there's no point in enforcing minimum wage for them.
Thanks for the neoliberalism in a nutshell post. Go ahead, bury your head deeper up your own ass instead of dealing with the reality of the economic situation in which we all find ourselves. I got a job as a "temp" once. I was working full time second-shift in a fucking factory, doing RMA services for a major laptop and tablet manufacturer. I was doing advanced troubleshooting and repair, with no benefits or security. Capitalists are, en masse, exploiting this stupid idea that somehow, people should be paid less for the same work because of what they intend to spend their pay on?