RolStoppable said:

....about half of the people in this thread don't even know that there's a difference between carts and cards.

It wouldn't surprise me to learn that half the people in this forum have never actually touched a cartridge.  It has been about 25 years since a non-Nintendo system used them.  

With that said, the fact that the words are being used interchangeably in this discussion does not mean that people don't know the difference. It's one of those things where one person uses the wrong word, and others repeat it without thinking.