I think economists have debunked the idea that working hours are zero sum and that reducing them (eg, to 35 hours a week from 40) gets you more jobs.
I would assume it would be much cheaper to pay 1.5x for extra time than to hire more employees. More employees means benefits and additional work resources (desks, phones, computers, office space, supervisory time, etc).
I think the blue collar OT incentives are mostly about low pay to begin with -- they don't make much money to begin with, so the OT is seen as welcome additional income. With otherwise well-paid white collar workers, there would be less of an incentive but that's highly individual -- I'm sure there are many people with kids in college, people that want a new car, etc would love the extra pay.