The MT contractor where I work deems it the cheapest solution versus the maximisation of profits.
Which reminds me of the old story about the young salesman complaining to the Fleet Manager, "Anyway, why do I only have a two door Fiesta?", to which the reply came, "Because, son, Ford don't make a one door Fiesta"!
Somehow, reading this thread, I can't help longing for the days when the Coxswain of an Admiral's barge doubled as his driver, and Flag Lieutenants to Naval Air Command Flag Officers doubled as their Personal Pilot, and were specifically appointed as such in the Officers' Appointment List.
Jack