Power draw specs overrated?

why does the power draw specs on videocards overrated? 9800gt advertised needing 26amps. but in reality, it just needs around 12 amps. gtx260 advertised needing 36 amps but it just really needs around 19.. dont know the advertised rating of the 4850, but my cousin said it just needs around 10-12 amps also.

Total system power requirements. Including hard drive, CPU, sound card, motherboard...

Power requirements are typically greater than what most people's system will draw. AMD and nVidia usually set higher specs as a safety margin and because they don't know what people have in their system.

Example: You and your friend wants to install a GTX 285 video card in your system. You have an Intel E8400, 2 hard drives, an average motherboard, and a DVD burner. Your friend has an Intel i7 940, 4 hard drives, a performance motherboard and two DVD burners. Guess who has higher power consumption before adding in the GTX 285?

Because it is reality.

Look at the diagram for the MB plug. A ton of them are 12V. Also look at the aux CPU power plug. I believe all of those are 12V. I'm afraid the CPU/MB uses a lot of 12V, just as the peripherals use 12V and 3.3V and 5V. The fans do only use 12V.

oh.. so whats the use of the other rails then?

mobo uses 3.3v & 5v
PCI cards draws from 5v
RAM draws from 3.3v
HDD & Optic drives draws from 12v & 5v
Floppy Drive (thought these died along with the dinosaurs) 3.3v