Awkward conversations...

So, yesterday while out for a walk I ran into an old friend. Funny to even say that...old friend, like we're 90 or something when in reality we are both pretty young. But anyway I say old friend because it has been at least 6 to 8 YEARS since we hung out. I've been out of school for six and we eventually grew apart even before we got out of school.
Anyway, I use to know this girl like the back of my hand...and she use to know me. There was a point that our parents knew where we were and that we were together..yes i know that friends will eventually drift apart and we each move onto our own lives (in which she is doing very well) but still, I can't help but feel a little sad for what we use to have.
The whole point of this was that when ever we see each other now (which is about once a year she comes back into town to visit her mom) we are reduced to the awkward hello's...how are u and nice weather conversations. How did things get like that?! it's terrible.
I am like this with most of the people I use to be friends with...I knew the secrets of these people and they knew mine! (only childhood stuff but for us it was important stuff). I just can't help but think about what I would really like to say to her but instead we act like complete strangers just passing through..in fact I have had more intimate conversations with a complete stranger then an old friend.
Yes I do have friends and in fact my best friend from school is still in my life i get to see her twice a year due to her schooling being so far away and I also named my daughter after her...but I still miss the way we were all friends back in the day.I don't even have contact with some of the people I use to be friends with but all these people for the most part keep in contact with each other.
Its the conversations and the realizations that we are all different people now that make me wounder how this happened and if there would or could of been anything that we could have done to change the outcome. I have tried to keep in contact and make play dates and invite them for coffee but things always come up or they never show up. The friends I have now are awesome but we are no where near as close as the little click i use to hang with in school..another questions...why do we get so close to people through school?
I use to think that I would be with these people forever but alas...we are down to the awkward conversations.