None of these people have said why it's called cream soda! Well, I found out, and I also found out why you don't get brands of cream soda in soda fountains.
A "fountain" cream soda doesn't actually come from a fountain, and is just so much better than a "bottled" one, and is made on-site in a cup instead of mixed by a machine. A real cream soda is rather close to its name: seltzer water, a flavored syrup (most commonly vanilla), and cream. It is extremely good, and you can get it in some coffee shops. (I got mine at The Daily Grind in Statesboro, Georgia.) Putting a brand of "cream soda" in a fountain would be a monstrous travesty, as bottles of the stuff are only simulations anyway - the cream would probably go bad on the shelf if it were real. Not that soda companies are in any way adverse to the concept of monstrous travesties.
I was a bit of a bottled cream soda fanatic until I tasted one of these. Now, the manufactured stuff may suffice for a while, but it's gotta be the real drink for me, even with the typical coffee house charge doubling or trebling the price.