I have a sneaking suspicion that the VC selection process is more like a high school election/popularity contest than a disciplined process. It's been a few years since I've been in a VC meeting, but I doubt much has changed. There are a few genuinely thoughtful VC, but there also seem to be a lot that make funding decisions that really don't make much sense.
The thing i, though, that I don't think they'd have much better results if it really were about the numbers and probability of success. Once beyond a base level of competence, the type of person that can sell something, whether it be of value or not, to a consumer is likely to be able to sell that same thing to a VC.