The rules are and always have been selectively enforced, in every area of life. It's the difference between the rules on the books and the rules as actually "done."
How many times have you rolled through a stoplight, jaywalked, had a drink while underage or consumed illicit drugs, made a mistake on your tax filings, moved your pivot foot, cut a corner in a menial job or an ethical corner in a less menial job, held a guy's jersey when he jumps for a reception, etc. without being penalized?
Somehow - despite the constant disorder - society, sports, medical practice, the academy, etc. etc. manages to function. All rules are selectively enforced. The manner of enforcement has a lot to do with how people experience and/or characterize this selective enforcement.