However, we use Gitlab for our DVCS (kind of surprised that's not on the list!) because that was a) very easy to install and b) better value compared to paid offerings, based on our usage. Also it's for the developers only, so ramp-up is less of an issue even though none of us had used it before.
So yeah for a lot of companies it's just about value for money. OSS is certainly free to download but the resource costs for installing/operating/training/supporting are not.