Are procurement departments missing out on potential suppliers?

I work in Business Development for an eSourcing software provider, so I'm approaching this topic from the 'other side of the fence' - but it is one I am interested in gaining further understanding, and would welcome people's genuine opinions on the subject. A large part of my daily activities involves trying to make an introduction to procurement professionals via cold (or slightly warm) calling! In my time, I've been told by some organisations that they do not accept cold calls, which has raised a number of questions in my mind: Does, or has, anyone worked for an organisation where this policy was in place? What are the reasons for this policy (is it purely to do with the volume of calls received, or perhaps, not received)? How would you typically find new suppliers if this policy was in place? Do you think that buyers are missing out on some potentially great suppliers through the implementation of this policy? Or does the reward outweigh the risk?