I work for the University I attend. The university is forced to buy computers under state contracts because it is a state university. Whoever made this particular contract with dell chose computers with the OS pre-installed on them. It's not a big deal though and since they come with Dell's volume-license, we don't have to update our volume-license.
Haha, that's pretty dumb. Especially in a situation where someone is managing a bunch of computers, they're going to want to build the OS from scratch so the network is more universal. This summer, we've signed on a four-year lease for 106 computers from DakTech (that's a lot of a district this size/budget). They don't have pre-installed OS'. I don't even know if it was an option.
DakTech is awesome, by the way. Seven year warranties are amazing. We have a couple of dual 1.0GHz servers. One of them had a disk in the RAID that was going bad. I called them, explained the situation and two days later, there was a new drive in our mailbox.