The politicians know this of course, but too many of them (mostly Republicans) don't care. They don't view low-wage workers as their constituency. Their policy (commonly called "trickle-down) is designed only to protect the rich. Fairness and economic justice are not terms to be found in their vocabulary.
Most Americans know the minimum wage is far too low, and a significant majority of them would like to see it raised to at least $9 or $10 an hour. But I wonder how many of them realize just how poorly the United States rates when compared to the rest of the developed world on this issue. The chart above is from Kevin Drum's blog at Mother Jones. It shows the minimum wage of each of those nations as a percentage of that country's median wage (the wage at which half of the country will make more and half will make less).
Note that only two countries have a minimum wage that is a lower percentage of the median wage than the United States percentage. Those countries are the Czech Republic and Estonia, and they only have a slightly lower percentage (36% instead of 38%). The other countries have a minimum wage that is a higher percentage of their median wage (ranging from 42% to 72%).
This is nothing short of embarrassing, and makes the United States look like a nation with a stingy and uncaring government. It wasn't always this way, but it is right now -- and it will stay that way as long as the GOP remains in control of any branch of government.