I wouldn't say they're trying to push <i>for</i> mobile desktops. They're trying to sell a product, just as they're tring to sell every other type of computer. There's a market out there. I know several people with desktop replacements, and several people who hate the idea of a huge ass laptop.
BTW, if you have a latop with a dvi connector, you can get a dvi to hdmi cable for ~$20 (or you can find a connector for ~$10 and use your own hdmi cable).