On one hand practically no (I'm not aware of any) servers from 1st tier vendors (Dell, HPaq, IBM) come from the factory with DVD drives today.
External USB DVDs are always an option but may be tedious in a datacenter environment, you'd need a kind of "crash cart" to hold your drive while it was hooked up to the server. This is exactly what I've done for blade servers.
On larger servers you could always swap the CD drive that came with it for a DVD but on the smaller 1U & 2U rackmount server often they have low profile (notebook style) CD drives that are probably harder to get a replacement for. & replacing the optical drive on my brand new server is not something I'd prefer to deal with.
Of course if media started being available on DVD only that would motivate the hardware manufactuers to include DVD drives with their servers.
Finally, I suspect that most people copy their installation media to the network and install from a local folder on the server anyways, and practically all notebooks and desktops come with DVD drives so it doesn't matter that much, except maybe in a DR scenario.
Microsoft
