In the same way, the chance of us having a nice chat with the CEO of Goldman is fair, but the chance of him maintaining contact with us and being a friend or mentor is pretty low. You don't have the money to hang with him, you don't have the opportunities to share with him and so on.
So you can get a date with the top model if you're brave. You can get a coffee with the CEO if you're brave. But I doubt that anything long term will develop, unless you have true value to offer.
And people evaluate their actual value and see that it probably is not enough to make it worth their while approaching this person.
An example that I'm sure many here can identify with: How many of you have emailed Paul Graham asking him for feedback on your app or whatever? Some brave ones likely have, but how many realistically expect a relationship to develop out of that?