Wii doesn't output 720p.. best it can manage is 480p with component.

to plug in a controller you need to remove the cover to easily plug in controller/mem card (sitting horizontally)
easy to lose probably, mines just sitting loose beside it

If you used your Wii for GameCube games you would probably have at least a memory card left in the top of the console more or less permanently, if not a couple of controllers as well, and the flap is designed to be easily removed so you can take it off and leave it off, rather than having it just hanging off the side, as obviously it won't close if anything is plugged into the top. So I'm guessing most of the missing ones are from people who have removed it and then just lost it, which would be easily done unless you put it in a safe place and remembered where it was years later (I kept mine in the Wii box so I knew where it was and could put it back on before I sold it, but then I'm probably in the minority of people who keep boxes for everything and store them safely).

Because when you plug the GameCube controllers in you need to remove it, and after two years they've always been thrown away by mistake.

Requested it to be unexpired.

You could try CEX, they have them for £24.50 delivered. Or like Cupcake posted he got one for £10 from eBay recently so give that a look.

Getting one for this reason also