Hey... I have a question.

I have a PSP since a year back, and recently I finally purchased the PS3. When I plug the PSP to my PS3 (via usb) it automatically detects it as a PSP and enables me to acces it's memory (videos, music, pictures) But why can't I play PSP games through my PS3.

I realize that it might be a stupid question, as Sony wants to keep the two systems apart. Forcing you to pay for a game twice.
But why then go through the effort of making the two units recognize eachother?