Why there haven't been cheating devices as of late...
While the official reason is that since gaming has gone online, there's no need for cheating programs for obvious reasons. However, I think the real reason is more complicated, but I can distill it down a bit.
- Console firmware is more like operating systems, which implement security levels. System level changes, like modifying another program's data, requires higher privileges, and most games and programs are probably built either isolated from everyone else, or purely low security level programs.
- Console manufactures forbade them to do so out of security reasons (if you can muck with any arbitrary memory value, you could invoke exploits).
- It's just harder to figure out where these values are. Or they implement the same thing Tri-Ace games have done.