One of the ideas floating around is that the economy is currently limited on the demand side, and that increased wages will result in more disposable income and higher consumption.
Increasing wages will make employers less inclined to hire people, and thus potentially less total disposable income. Giving ordinary people more money directly seems like a more reasonable sort of stimulus. Where are these ideas floating around? The idea of sticky wages dates back to Keynes.
I tend to side with the argument that employers ultimately hire not because people are cheap, but because they need them to meet demand. If there's no demand, there's no wage low enough to justify a hire. I don't want to speak for Thomas Piketty, but my reading of his data is that generally economic growth is the product of higher wages, not the other way around.