Speaking on behalf of the younger parents on this board, my 3 kids do a combination of both to my wife and I.
I've spent more time playing with LEGOs and learning about superheros over the last few years than I ever had as a child. I haven't been to a non-animated film in the theaters for almost 4 years, and don't really mind waiting until Redbox gets the Academy Award movies for me to see for the first time. I keep myself healthy and eat well partly for my own self-consciousness, but also to set a good example (I couldn't make them eat veggies if I didn't eat them myself
) and to do what I can to maximize my time on this planet with my kids.
But I've also "grown up" a lot faster than many of my childless friends.
Setting up college savings accounts. Writing living wills. Life insurance policies. Health benefit coordination and planning. Minimizing and killing debt. Homeownership and establishing roots in a community. Evaluating school districts in regards to where we want to live. Being able to function with no sleep.
Obviously I have friends that have done some of these things, too, but I'm quite sure I wouldn't have done them as quickly as I did, or realized their importance as quickly, had I not had children.
NOTE: I'm not saying that childless people are immature. I'm just saying that I was thinking about future planning, etc a bit sooner with kiddos in the picture.