Let me rephrase: what are the drivers that keep it so low, such that the "democratic" system in the US feels that level to be adequate for a minimum wage?
It's the
federal minimum wage. States do their own things, but if we think, for instance, of the last however many decades of a bad joke called, "Jobs, jobs, jobs, j'abortion!" that's how it happens.
Even if Democrats hold the House, they need sixty votes in the Senate. This is why the culture wars: Who really thinks conservative working class voters are going to say, "We're voting for Republicans so they can wreck us!" For these voters, there is always a woman, or a gay person, or a transgender student, or a Black person, or a Jew, "Mexican", Muslim, or Native American to blame. There is always something wrong.
And there are some object lessons in Democratic Party history: It's one thing to suggest it's never been a truly liberal party, but if you recall Sen. Zell Miller (D-GA) pandering to the 2004 Republican National Convention, or Sens. Kyrsten Sinema (D-AZ) and Joe Manchin (D-WV) in the current Democratic caucus, we see what it takes to for Democrats to satisfy voters in those states; it's also why Blue Dogs exist. Think of the idea that in conservative states, workers hear the argument against unions, see the data showing union wages and workers fare better over time, and then vote against unions in favor of a slogan called, "right to work", which results in lower wages; the bourgeoisie and petit-bourgeoisie are not sufficient to carry the vote without significant support from the working class.
An extraordinary anecdote: Once upon a time, I had a strange conversation in which the question of how to win over voters who are so determined that they will vote against their own best interests fell away to a somewhat predictable dispute about the elitism of presuming to know someone else's best interest, but on this occasion it really was so clear. Suffering to death is, by definition, an antithesis of one's best interests. What do you do about voters who will literally hurt themselves in order to not vote for you? The examples at hand were Bevin in Kentucky, 2015, and Trump, 2016, and voters who would lose healthcare access if Republicans wrecked or repealed the ACA. And, sure, that one conversation is an outlier with particular contributing factors, but what makes it extraordinary is that it's usually not so straightforward. It's not like these attitudes, either about liberal elitism or, as we heard in the 2012 Republican primary, letting them die, are new.
Say what we will about the federal minimum wage, but voters in conservative states are far too worried about registries and search warrants for menstrual cycles, censoring education, and fiddling with election laws.
They've been voting for these politicians for years. Generations, even.