I won't say that students never cheat, either at a two-year or four-year institution. It's one of those things that a teacher has to watch out for. (In my case, I try to make my assignments enjoyable enough that no one would want to cheat... and when that fails, at least making assignments where it would be impossible to get someone else to do your work for you, like giving an in-class presentation.)
However, the methods of cheating differ between community college and a more typical four-year university. Honestly, policing a class at community college is much easier.
At a four-year school, there are student dorms, and fraternities and sororities and student clubs, all places where students can save old assignments and tests to form a study bank (which forces professors to vary their test questions, or else have some students who suspiciously seem to know every answer as if it were memorized...). Most students have a social network of friends and they typically study together, which opens the door to having them do each other's assignments.
At a community college, ironically, there is no community; it's a day campus only. Students may have friends, but a lot of those friends aren't fellow students, so there's less group study. Most students don't stay around longer than two years, either, which limits the amount of old tests they can pass on to the next "generation" of students (since this generation is only one year behind them).
The net result is that it's easier to repeat test questions at a community college, without fear that my students are going to walk in with a study sheet cribbed from last year's exam. It's also easier to request that homework assignments be done on an individual basis, because a lot of students don't have the means to work in groups anyway.
Of course, the down side to this is that assignments that require work in a team outside of class are much harder. As with everything in life, there are tradeoffs.