>>720693015 (OP)
Blame a part of it on Achievements and online features/components being the standard. Leads to potential for $$$ to be made.
Also, lots of games nowadays are online/co-op and built around that pretty much, how can we work cheat codes into that? Obviously it'd be a problem for competitive games, but it'd seem annoying for even co-op games.
That being said, With many cases on what would've been a good idea for a cheat code in some games, would already be worked into the natural gameplay itself nowadays. Like with any other craft, different groups take what's proven to work..and blend some of it into their own. Over the decades devs basically phased-out them out.