"Of course the mother doesn't HAVE to take time off - just do a planned c section on a Saturday and she can be back to work on Monday."

This isn't based on reality. Recovery time for a c-section is a week or two at least (planned or emergency). I would think 5-6 weeks before anyone would be talking about going back to work.

It's a major surgery.

Only way you could do a Saturday delivery and back to work on Monday is if you were a superhero and dropped the baby the classic way early AM Saturday.