I'd say whether you invest your money or spend it on things now depends on the degree of benefit you get out of either activity.
If you're a 'Bill Gates nerd', of course you're not gonna blow all your money trying to chase every woman that you come across because frankly... you're not getting back as much as you put in. In other words the utility you get out of taking a trip to Europe or Asia, or partying, isn't as much as the satisfying feeling you get out of seeing your portfolio GROW BABY! In this case shares are actually SEXY. Hey you might even be thinking about pleasing the ladies further down the track......... You're just waiting for the right time!
However if you regard yourself as some kind of Sex God in the traditional carnal sense, you're young, full of life, and ready for some summer lovin', then of course you're gonna buy cars, take exotic holidays and please the ladies NOW. And money won't seem so precious to you. You're not gonna slave yourself to the system yet (but you know you have to eventually). So you csah your chips now and spend.
It all depends on "utility".
But that's also why the nerds eventually get their revenge later on, when they see their old cool high school friends slaving over a mortgage, a car loan etc. in their 30's!
These are extreme examples though, I'd say most young people fall in between somewhere!