People in the profession/career set the bar with their own example over time. Hockey players have never demonstrated the finesse of etiquette that tennis pros have demonstrated. Presidents have been historically been measured by a certain bar of ethics and honesty, education and knowledge, compassion and grace. There is no LAW that says any of these standards need to be adhered to by anyone in a given profession. Today's tennis player might change the perception of what is/will become acceptable for other tennis pros. Remember Jimmy Connors, the "bad boy" of tennis, and how his "outrageous behavior" changed what the next generation of tennis players grew up expecting. President Trump is demonstrating that just because a person is the President, there is really NO firm expectation of ethics, honesty, education, knowledge, compassion or grace that will be applied to the office and, failing to achieve that "bar," no punishment for it.
As for heads of corporations? They've had a history of cheating, lying, manipulating, and swindling. There's your bar. Or perhaps it's not so much a bar as it is a barf. Regardless, it's the historical model and that's where the bar has been set.