When you are young, you think older people know nothing. They are from a different generation. They don't get it. As you start to grow up, which really doesn't happen till you are into your 30's...or 40's for some, you start to realize that you don't really know what you are doing and that you should have listened to your parents' advice 10 years ago.
And now that I am in my 30's, I try to tell those kids who are close to or in their early 20's to listen to the older generation (and I'm realizing that that generation thinks I am the older generation - sigh). It is often in these younger years that we make some of our most important decisions: higher education, career path, marriage: all potentially lifelong decisions. And we are too young and inexperienced to make those decisions!!
Now I'm not saying that every older person you chat with is going to have great words of wisdom. As a matter of fact, you might find out some choices they made that you don't want to make because you can see the outcome in front of you: family relationships ruined, habits and addictions that are hard to break, and broken marriages.
But, if you listen, you will understand that there are many years of experiences talking, a lifetime of decisions that affected this person, hurt and heartache, love lost and love gained, so many memories to draw from, all building wisdom. And if we choose to dismiss the older generation, we risk the chance that we are throwing away a wealth of wisdom to draw from.