I think its more because old habits, like Silicon Valley's gentleman's club, die hard. There are tons of excellent hackers who couldn't get an introduction, including a large number of the Y C companies that went on to get VC funding.
I know from a talk that one of the VCs at Sequoia gave that almost nobody gets funded by them without having been introduced. He said that they were meaning to pay more attention to stuff that comes in over the transom, but it sounded much like I do when I say that I want to work out more.
