I respect your opinion Jesse, but I could not disagree more.
Unwritten rules are there to protect players from making errors in judgement and to keep minor offenses from escalating into on-field brawls. Unwritten rules are followed or punishments are doled out, be it from opposing players, umpires, the media or league officials.
Unwritten rule: Catchers shouldnt block the plate without holding the ball. That rule was so obvious that it became a written rule. Would you have every catcher stand in the path of the runners? Of course not. But because some folks didnt abide by the unwritten rule, it had to be formalized.
You mention stealing with a big lead, this is a very common and important unwritten rule. But you claim its nebulous and accuse fans of a lack of understanding by even using the term. Yet professionals know it is defined very clearly "if you have more runs than outs left in the game, dont run". This is another unwritten rule that became a written one, scorers indifference was not among the original scoring rules but has become an obvious result in blowout games. League scorers got sick of rewarding baserunners who didn't observe this unwritten rule and so it got written down.
Other unwritten rules became written, thats why coaches and catchers have to stay in their chalked out boxes to reduce interference. Originally it was thought that everyone knew not to interfere with the players - it was an unwritten rule. Pitchers with a foot on the rubber? Same. Don't gamble on your own teams games? That one had to get written in pretty early on!
It was unwritten not to throw at players heads. But some folks agree with you, that it wasnt written in the rules so why not do it? Black marks on character didnt keep Bob Gibson from being the most feared and successful pitcher on the planet, so those unwritten rules had to be written out to protect players. Now umpires eject pitchers they feel intentionally throw beanballs.
There is a "right way" to play the game, simply that is to respect the opposition. To ignore this rule is to flirt with danger on the field. What happens when a pitcher throws at a players head? The offended batter takes issue and charges the mound. What happens when a player upends a middle infielder with a late slide? Brawls break out, umpires eject offending players, fans boo, newspapers write accusatory headlines.
Are you advocating late slides? Pitching at heads? Blocking home plate? These unwritten rules are universal in spite of any claim that players from different countries are raised with different unwritten rules. Where do they let these guidelines slide? Nowhere. Period. Baseball is played worldwide and disregarding them gets the same result no matter where you see the game. Etiquette is not varied by countries, only the method of punishment and retaliation.
By your argument, you have no issue with a batter not running out a popup? Running hard on a groundball that is a sure out? Stealing a peek back at the catcher to see the signs? Every fan in the world knows those are things players should do every time, no matter what. Unwritten rules are wide ranging and effective.
How about ones that affect your job as a media contact - do you get irked with players who dodge interviews? How would you feel if they call the pressbox during a game to complain about your play by play? Do you expect them to hear your criticism during a game broadcast but never say anything to the public about it? Those are unwritten rules that players face as well, but less is said about them because the media is the disrespected party and doesn't share that they were insulted. Yet, you surely know that it often affects a return from the offended party just as a late slide or beanball would. Thats why some teams announcers have been bumped from team charter flights as punishment, a war of attrition just the same as two teams throwing beanballs until the benches clear.
Bat flips are not respectful, pitchers pumping fists after strikeouts mid-inning arent either. The unwritten rules must be followed, or you will eventually see chin music or be met with Brian McCann as you try to cross home plate. I mention here Chase Utley, who didn't break any written rule with a late slide but still faces suspension, which proves even MLB HQ frowns on players who shun unwritten rules.
Unwritten rules are common and must be followed. If they aren't, they become written rules. Fans using the term are simply acknowledging that they see a player disrespecting the opposition. I think it shows the human inclination to judge morality and integrity in others.
When you get down to it, historically speaking EVERY rule was an unwritten rule until it was so flagrantly ignored that it had to be written down.
Simply put, unwritten rules run the game and if they get ignored too often they get added into the rule book to protect both players and the integrity of the game.