The typical fast food employee makes around 20K/yr, and most cooks can only command up to 30-40K without certifications. The constant supply and ease of training cooks (not chefs) keeps these wages depressed.

Trucking wages are not the greatest, but it feeds your family and pays the bills. The cost savings may be small but coming from a small town where 1/4 of the working population has class 3 and class 1 licenses operating these machines. It's a middle class lifestyle for these communities.