Using Sessions in vBulletin
 

I'm looking at the code for vBulletin and I notice that they don't use PHP Sessions (session_start, etc...)

Is there a reason for this? More importantly, I want to implement a mod that gets some information from the session (unrelated to vBulletin... I'm trying to get user info from my own site...). Is there some standard that I don't do that, or is it cool to do that?

Any help is appreciated, thanks!!