The adult world gets to be a tiresome place sometimes. Yes, there's definitely the upsides (a driver's license is but one) but for the most part the responsibilities and cynicism and existential grinding can make life feel like a burden.
There's a certain brightness and sweetness to youth, a way of understanding things before reality intrudes beyond where it should. There hasn't been the rejection from a would-be girlfriend or the horrendous calc test or the miserable performance review. There's the fun of doing things just to do things. There's the ability to live and not even have to be convinced that the next day is going to be good. We should all try to be a bit more like that.