However that does not explain why J* staff attrition has been double that of mainline for the last 5 years.
The low cost business model allows for employee turnover. Basically it is cheaper to train a flight attendent, have them leave after a few years and train another, than it is provide attractive terms and conditions so they will stay long term.
Managing staff turnover in order to stay on the right side of the "lift/drag" curve is part of the game. Managers need to know how little they can get away with paying before turnover costs becomes prohibitive.