The way it does this isn't by paying workers more than competitors do for the same work. It's by charging customers less than competitors do, which actually selfishly benefits them by increasing their market share, but also distributes more wealth to workers because you can buy more for the same dollar (or the same amount of stuff and add to your savings or pay down debt).

What prevents this is uncompetitive markets, which are occasionally found as a result of natural monopolies, and more commonly found as a result of regulatory capture.