copla, I appreciate your point of view and consider it sound, but I'm not sure it's that black and white.
It's obviously ideal to have your life "figured out" prior to entering college so you can decide whether it is necessary. You want to be a lawyer - yes, a writer - perhaps not. Many people simply can't be that clear about their purpose at that stage in their life, but even if you convinced me they could (and should) be w/ some introspection, what about the reality that their purpose may change in the future?
Say someone wants to be a writer and turns down college because it's not worth it, and by all accounts they become successful. But in the process this person learns about the legal process involved with copyrights and publishing and gets inspired by some people they've worked with and decides they would serve a better purpose as a laywer in the publishing business. Ouch. But they have no education, so they must endure 4 years of college before they can even take their first class in law school.
Surely, it goes the other way too - this may not be the best example. The point is, if you either don't have a purpose or expect the chances of it changing are likely, the concept of "If you don't know what road in life you want to take, then it doesn't really matter what road you take, as long as you don't stand there pondering your life away because you can't decide which road to take." is a reasonable one.
What's that Lennon quote? "Life is what happens when you are busy making other plans"
I agree it would be better to have decided upon your plans and begun to implement them, but if you haven't it's not a bad idea to go ahead and just experience life (going to college, in my example) as long as it's in a direction you think would be of benefit in the future. You could waste as much of your life "making plans" (finding your purpose) as much as you could "experiencing life" (just doing something). There's a balance.