Fools
Wages are so low because they can find fools to do it for so little.
Anyone who flies a twin turboprop for less than $30,000 PA is VERY foolish, and is doing enormous harm to the industry. I earned $43,000 for flying a twin turboprop in 1992.
I think many do it because they think they will get into a big shiny jet next year. Those who have not got some sort of committment from an airline should think hard and long about what they are doing. It has been stated that the airlines only accept one in every hundred applicants.
So you should only accept jobs that are properly paid, and consider it long term. If you do otherwise, then blame yourself, and don't complain, because you are adding to the problem.