Why would I want to take over the TV so that nobody else in the house can use it to watch TV?
Because that way they can play a video game with you without necessarily having to buy their own gaming PCs and their own copies of the game.
What wrong with a wireless keyboard and mouse?
KB+M is fine for single player. The problem comes when you have players 2, 3, and 4 visiting your home, and the APIs for accessing more than one mouse or more than one keyboard are far more obscure than the APIs for accessing more than one gamepad.
We're taling about HTTP and HTML, not the web.
What's the difference between the HTTP and HTML on one hand and the web on the other?
WebGL is fine.
From this page, Atom N450, Xubuntu 12.04, Xorg 1.11.3, Firefox 24: "Hmm. While your browser seems to support WebGL, it is disabled or unavailable. If possible, please ensure that you are running the latest drivers for your video card." This Mozilla page recommended looking in the "Additional Drivers" utility that came with the operating system, but all it showed me was the driver for a Broadcom NIC that I'm already using. The Mozilla page also referred me to Intel's driver update utility, but that's Windows-only.
Because it ships with a gamepad and has a case designed to fit in next to a television.
Neither of those is terribly remarkable in this day and age.
If you'd believe an Anonymous Coward's side of this story, then shipping with a gamepad and being marketed for use with a TV are remarkable because they are beyond the lowest common denominator for PC gaming. Is this AC right or just full of crap?
The solution of this problem is trivial and is left as an exercise for the reader.