From its inception, increases in the minimum wage have
always be accompanied by increased unemployment rates. The impact is usually placed on the young, inexperienced, often minority, worker...the very demogaphic unit it's supposed to help. Given that unemployment effect is as certain as the rising sun, why would politicians continue to think they can outperform a free market? The reason is because you have incredibly stupid people like those shown in the photo above who believe they can subvert the laws of supply and demand with impunity. The best that many can hope for in the long run is to say: "I can make $15/hr...if I can find a job."
Idiots.
Given that unemployment effect is as certain as the rising sun, why would politicians continue to think they can outperform a free market? The answer is that they don't. They're interested in votes, not jobs for marginal workers. They know perfectly well the effects their policies will have, and they do not care.