It's not quite as simple as that though because those people you refer to as "patsies" respect the rules as long as they are not in a minority that suffers because of the rules. Identifying as one of those sufferers requires experience, i.e. the person may have been stung more than once with gate-check fees due to being at the end of a late boarding group. A sufferer is more likely to break the rules. Infrequent flyers are therefore unlikely to break the rules.

A small number of the sufferers will never break the rules (as you mentioned) because community cooperation means more to them than personal gain. Given the lack of penalty for cheating it is not likely that this is due to fear of consequences but probably a lack of desire to disadvantage the group as a whole.

There's a third group though, and that is pax who have checked their luggage already and only have small items of hand baggage. They are unlikely to become sufferers as there's no trigger for that, and therefore they're unlikely to become rule breakers, but they're not patsies either. This doesn't mean they wouldn't be one or the other if the trigger was there, but they're not exhibiting that behaviour in this circumstance.