I would see myself ordering a bunch of Ubuntu systems from someone like Dell if I were a large business issuing them to my employees. Since I'm small, I always roll my own. I see the reasoning behind their decision, though I don't have to like it.
IMO the best way to get Linux in the hands of the masses is through devices that almost replace PCs, but aren't PCs themselves, like phones, tablets, home media servers, etc.
The problem: As an "enthusiast/advanced user", why would I buy a Dell laptop pre-installed with Ubuntu when I can get a Windows license and install Ubuntu whenever I want?
You'd buy one with Ubuntu if you didn't need Windows and didn't want to pay for a Windows license.