Because of demand and supply. But there are many more "shitty" sectors, that are absolutely vital and underpaid. That showed quite nice at the pandemic, where vital workers got excemptions from the lockdown. Those vital workers were mostly all the low paying jobs. I think that got some people thinking, at least for some minutes about the absurdity of the status quo.
So I am all for paying them all more and for example the executive of the german train (who had his company have a shitty year in the reds, but still effectivly doubling his salary) less.
Suggestions on how to actually change it?
Most approaches I know where people go to the top to change things kind of fail, - once they are at the top, they rather enjoy the benefits there. Whether they are socialists or free market radicals.
In US cities with highest costs of living, the laws of supply and demand are already fixing the issue. The lowest paid professions in there pay $20 per hour or more, so basically twice than in areas with low CoL.
You should pay enough to live in the area you work in. If that means that the jobs pay more than someone that needs the degree to work in their field, the person with the degree is being underpaid as well.
FWIW: Some of the garbage men, janitors, retail employees, and others working in "unskilled" jobs likely have degrees too. This is even more likely if they are immigrants.