Because I don't know of any current mainstream CPU that isn't 64 bit. There's no reason to specify that when when it's just a forgone conclusion.
As far as motherboards go, there's no such thing as a "64 bit motherboard", so labeling one as such would be nonsensical.
Edit: With that said, none of that really means anything. It's not like you can't use a 32 bit OS or 32 bit programs on a 64 bit CPU because you absolutely can.
Edit 2: I didn't see that you made two posts on this, but the other post had replies that told you exactly what I did.