To be honest, I resent the implication that 'sports' and 'girlfriends' are the normal high school pursuits and everything else is squandering your youth. I also dislike the suggestion that you should strive to be normal, or that only doing fun things during high school is the right choice. It strikes me as an incredibly shallow and short-sighted bit of advice. I don't have anything against sports, really -- fitness is good, and sports can be a big door opener if you're serious. But I have a huge problem with telling our younger audience, hey, spend your time on frivolous stuff and come back when you're older. That's not right.
"Normal" is an ambiguous term, you should have probably used "average" in your description. Even so, "average" is quite relative, so sitting in front of computer all the time being good for you might not be so for someone else.
However, you only described the problem but did not provide any solutions. I agree that some people who can easily find their passion, which could help their career, could very well do it on their own. For instance, I work in IT sphere and it's something I enjoy, therefore even when I work, I have fun. In fact, I get a lot of pleasure for finishing projects and getting things done. Yet, there are people who might not be that focused (e.g. some people who work with me), who cannot accomplish a single thing without proper guidance. Therefore, motivating some people to do things, either for work or for fun might not be such a bad idea after all.
On the other hand, I would rather let my kids spend more time with the family or even sit on the computer more often than get AIDS from having unprotected sex with random gals or get drugs from random "friends", but that's just me. Everyone is free to do what they consider best.
In my own case, sure I've sent more time with the computer and books, but I did have a lot of fun when studying for engineering career ten years ago. For instance, we went to ACM programming contest on the institute's bus, we got pretty drunk and made a lot of trouble while other teams were laughing at us - the same day my teammates went to the strip club, while I was calling my ex and making a mess. Next day we went to the contest with a huge hangover and diarrhea (from local food); we returned from the contest with 1st place award and this time the other teams were not laughing anymore. Moral of this story? You can still have fun and accomplish wonderful things (but if you are wondering, I haven't had an alcoholic beverage for 4 years now and *that* I don't regret).