Not everybody wants the same thing in a job.. For some people, 30 hours and a flexible schedule might be perfect. If you need a job that makes you self-supporting, one 30-hour job probably won't do it for you, so you have to keep looking, or find a second job or revenue source (babysitting, landscaping, dog walking). Taco Bell doesn't owe anybody a middle-class lifestyle - only a fair wage for the work done.
I was in retailing many years ago, and my discount-department store employed about 40 women, working from 1000 to 1400, M-F, and for them it was perfect. It was a second income that allowed them to be home when the kids went to school, and home when they got home. The combination of the modest income and the employee discount was a big help to their households. Could they live on that money? No. But it was still a good job..