You're basically imply that there's no substantial difference between a regular OS (OSX/Seven/Ubuntu) and one in the PS3?

OS that need to do anything (PC OSes) and OS made for just few thing (gaming&multimedia for VG console) are both heavily optimized.. but in different directions.
It's pretty improbable that you will able to print documents with a ps3 (when you start a game all services get stop.. so even an eventual printer service)... music change if you put linux in a PS3, then with CUPS.

But the PS3 gamers don't give a f~~ about CUPS.. they want a kernel that run God of War smoothly and fast: so the PS3 kernel force all the hardware to serve resource (cpu/ram/bandwidth...) for gaming.