That was an extremely astute observation!
There's not much I can add to it, but as far as the wisdom thing, it's not that you're not absolutely correct ... however, there is more truth that goes along with it.
No matter how much you know or are able to comprehend, there are some things that only experience can impart knowledge. That is why the saying goes as it does. It's not that a 25-year-old can't be "wise" but, it's hard for one to be as wise as a 35-year-old, because there are things that the 25-year-old simply hasn't gone through yet ... the 35-year-old has 10 additional years worth of time to have gathered that information. And the more you know, the more you know. You know?