If they offered cheat codes for one thing. Another is that games get passed around and instruction booklets get lost. So, if they offered a PDF download of instruction books, that would be a help. It really shouldn't take that long to scan in a book, and if they offered this to non members as well, word would get out and possibly attract new members.
I would love to have just one website to rent, buy, check out the cheat codes and download a lost instruction manual. It would save me a chunk of time for gaming.