This was what I was told re CS:
Driving: You aren't covered by your insurance to drive within 72 hours of a general anaesthetic (which is what I had). So it's actually only illegal to drive within 5 days. I moaned at my GP about 3 weeks (large rural parish) after my CS saying I was going stir-crazy, and he said once you are on the mend, can manage to look right over both shoulders (checking blind spots), can fully depress the brake and other pedals, and can wear the seat belt, there is no earthly reason for not going back to driving, but to check with one's insurer first. I think the 6 weeks no driving thing is an urban myth.
Lifting: I was told no lifting anything heavier than than the baby for a week to ten days. Very luckily my incision healed extremely well so I was pretty much fighting fit again with a month (certainly back to driving).
I think the advice given is actually good advice- it helps you recover faster. There's no sense in doing anything too early that jeopardises your recovery. And certainly no brownie points in being up and about earlier than the next person. I spent DH's fortnight paternity leave in bed with the baby and it was great!
TBH I think I recovered faster from the crash CS with DD3 than I did from the birth of DD2, a beautifully straightforward 4 hour home labour, but I also had 2 other very young children to look after, before the days of paternity leave longer than 2 days, and neither of our mothers was available to help, so I was back to normal duties after 3 days. I ended up with mastitis after 4 weeks which I'd never had before and I put down to exhaustion.