Digitally Renting PSP Games?

During my travels through my new PSP Go, searching in and out of every nook and cranny to prepare for my hardware review I had noticed something peculiar: you can't group your games into folders like you can on the PS3. Out of curiosity I pressed square to re-sort the folders like the PS3; and it did. But there is only 1 way to sort them... and that is by when they expire. Why would my PSP games