UNLESS,
basic CPL junior FOs get considerably lower salary, their inexperience correlates with staying longer with company (more return on training investment) and more importantly, besides the salary savings, as compared to more experienced crew who may not want to slave for peanuts, they're more moldable and forgiving regarding any downsides, silly rostering, other T&Cs.
This is more general and may or may not apply to certain airlines, depending on country and union group strength (if there are any).