TD, do you know why it's only considered medically required for c/s?? What makes a saggy post-c/s belly different to a saggy post-vaginal-birth belly?

Just wondering as a good friend of mine had a c/s with her son a few weeks before I had DD1 (vaginally) and her belly's in better shape than mine - I know every person is different but I'm just wondering what the logic behind only c/s bellies qualifying for rebates? Is there something in the c/s procedure that does more damage to your abdomen (I mean, obviously, cutting through all that skin and muscle etc, but apart from that), but at the end of the day isn't a tummy tuck for aesthetic purposes?