Apparently you missed the point of the post. Fifteen dollars is still not a sustainable wage in most areas. Hence, people will still be sucking off the taxpayers for assistance. Companies will end up pushing back by automating as much as possible and eliminating positions.
Why should the government rock the apple cart by forcing companies to raise wages? Just as people have choices when it comes to working, companies should have a choice to value job duties how they want. If someone wants to earn more, then they have to work to do so. It is really not that difficult of a concept to understand. Many companies pay well for good, reliable talent.