Most of the time most rules are really arbitrary, actually.
Especially regarding table etiquette, or things as social etiquette. Why should I sit in a way or another at the table while eating or use spoons, knives, and forks in one way or another, even if those aren't the most comfortable ways for me, just because that's the rule? Why should I look people always to the eyes? That won't make communication better or easier, and just will be hurtful to me (literally, I can suffer from headaches, nausea, cold sweat, stomach aches, and other symptoms of severe social anxiety).
The problem with acritical rule following is that it will make you more prone to do bad things if a rule tells you to do so, just because "that's what the rules say".