Yet people will refuse the job of janitor because it's too gross or "under" them, and the job is kind of integral for society.
Being a janitor is part of my job description (I have to take care of the entire lobby). This isn't just mopping the floor and dusting shelves. I have had to clean up liquid crap off the floor of the bathroom far more times than I have ever wanted to in my entire life. Try telling me I don't deserve a living wage for putting up with biohazards on a daily basis (if it's not crap, it's pee, or blood, or spit).
I'm just being brutally honest, if being a janitor is so important, wages would go up. That is a fact. If your job was so hard and no one wanted to do it, they wouldn't be able to find a employee, they would increase wages to try to get someone. But the moment you quit, they can get someone right away probably.
The same isn't true for someone who is a doctor, lawyer, or a engineer. It just isn't. If a doctor quits, they can't just hire another for a low price. Why? Because it takes an insane amount of intelligence and hard work to become a doctor. And no one is going to go through medical school so they can earn the same wage as someone who didn't finish high school.
If what you are saying is true, that there isn't an oversupply of people who wants to be janitors or are willing to, then just quit, and I'm sure whoever you work for can't find a replacement without increasing the wage, and guess what wages will go up.
But o wait, the moment you quit, I bet the company can find someone immediately. Sorry, just the truth I believe.
The thing that ultimately determines price in the world is supply and demand, not how integral something is. If that were true, water would be the most expensive thing in the world, and it's not. Maybe if the supply of water drastically went down, it's price would go up. Heck if there was only 1 gallon of water left in the world, it'd be worth more than the Planet itself.