Perhaps it also matters that some students have more or less incentive to cheat.
Top academic achievers have less incentive to cheat if they can get good grades honestly without unrealistic effort. Some hooked students may not feel the need to cheat if their path in life is already bought (D and perhaps some L in the ALDC taxonomy), so gentlemen B or C grades are fine for them.
But would students on the margin of an actual or perceived grade or GPA threshold needed for some competitive goal like admission to major or professional school have more of an incentive to cheat?
Perhaps the mix of students and incentives matters in terms of whether cheating is common and how strict the rules have to be against it.