That is true of *any* group, a corporation, a street gang, a tribe, or for that matter, the Catholic Church or the Communist Party - not just the professions. If anything, the professions are probably less prone than other groups to favor arbitrary codes of conduct at the expense of technical accuracy.
For example, those who had the misfortune of serving in the army (any army) probably experienced being ordered to do irrational tasks, such as cleaning toilets with a toothbrush or sweeping stairs in the upward direction. Such tasks are not just expressions of the sadistic idiocy of drill sergeants (although that often is the case), but an important socialization ritual whose main message is: "You will do things solely because you are ordered to do so, whether it makes sense or not. In fact, it is not you who decides what 'makes sense' but your superior." In this case, soldiers are deliberately ordered to commit a 'technical' error to demonstrate the superiority of the code of conduct.
The more arbitrary the rule, the more strictly it is sanctioned by stakehoolders in the group. It is so, because the occurrence and adverse consequences of technical errors can be manifested i.e. "sanctioned" in a matter-of-fact way, i.e. something objectively bad will happen if an error is committed. By contrast, rules of conducts are "socially constructed" or arbitrary, and nothing objectively bad will happen if they are breached. Therefore, the strict enforcement of these rules by the stakeholders in the group is the only sanction available.
Sorry for overposting - this is the last one, really.
wojtek