Well... in my professional career i got to work for two years in Mexico. One of them as a Cenote guide. My point of view:
Personally I never took divers into cave zones, i did some blind jumps,if they can be called so, because they were allways done into the cavern zone. But i would say it is a very common habit to break those rules.
Why? Tips. Happy customers. Videos for sales. Your boss pushes you... there are many reasons why this is done.
I don't see Cenotes as a dangerouse diving. Actually i think it is very safe. Much safer than many other dives that are done around the globe.
Think that the first 5 to 10 first minutes of the dive usually happen on the open water area and its during this time that the guide or the diver can decide that he or she is not ready for the dive.
Of course would be lovely that everybody does the Cavern speciallity. Believe me, the guides would be the happiest ones about that.
It is not easy to deal with machos half panicking, crazzy overweighted "experience divers", vertical divers that the only horitzontal position they know is while sleeping or divers that believe that the frog kick is a kind of game were you kick frogs.
It is not fun to have divers that decide that they can just abandon the group for a nice picture or that they overpass you.
Guides would love to be able to make a cavern diving course to every single diver that wants to dive in a cenote.
I agree in the fact that a mistake can be fatal. An who pays the mistake are the divers. But allso the guide.
Cavern rules have to be well explained and respected.
And of course is all about the money. Dive industry, as an industry, is about the money, the dive centers are business not NGO and the tourism is about money aswell.
Whoever complains about dive industry as a money "thinker" is doing the same as if they were complaining because a supermarket wants to have benefits.
I hope you have some nice replys.
Happy Bubbles
Scuba Legends