It's not really a silly question, it's valid.
Yeah, the WiiU has a 75w power supply, and so tests have indicated that it "peaks" out at 33w usage.
http://www.anandtech.com/show/6465/nintendo-wii-u-teardown
Why would they only be using less than half the wattage of the power supply?
Some are saying that it's the efficiency that brings the "usable" wattage down 70-80% (which would mean usable wattage would be around 52watts. However, I believe these people are incorrect, because the rating on power supplies is what it can actually deliver, and the inefficiences actually are at the wall side (which would be an actual power draw of around 100watts at 70% efficiency)
So we *should* have 75 watts for use by the console.
Some other places the power consumption could go:
USB ports usually power up to 500mA, which is what the Wii U supports (which is why you need 2 ports for some external USB drives), that's 2.5W. There are 4 of these ports, whic would be 10W
I don't believe anandtech was maxing out the USB ports power draw, so now we're at 43W
I don't know what else would use power, since during a game, the disk drive is already spinning in the case of the WiiU, obviously all the chips and components are working, wireless antenna's and such.
Maybe the SD card slot? That would be another 1W or so.
So we're at 44W?
It's possible that Nintendo went with a cheaper Power Supply that doesn't have over draw protection, and thus over spec'd it to just be careful. Even so, it's a closed system, I don't think you'd need that much leeway.
*puts on fanboy hat*
There is still a chance that via a future firmware upgrade, Nintendo could up the CPU/GPU clocks somewhat, similar to what Sony did with the PSP (didn't Nintendo also overclock the 3DS post launch as well?). Or maybe there is some silicon that hasn't been excersized in some games as of yet. Or maybe the disk drive isn't spinning at full speed yet (or ever will due to noise/durability?). Who knows... just believe!
*takes off fanboy hat*