I think you underestimate the areas where full (or significant) staff is needed. What about manufacturing jobs, farming, transportation and logistics (especially transportation of ppl not goods), services (including public services).

I'd say all the services which require face to face interaction will become way more costly if such buffers will be needed to cover off hours. For example: there is a notion of skeleton crew and the service might not be operational without that crew so the choice is actually to spread the cost of off hours low load to the high load hours or close the business for low load hours.