Hanging out in a bar once, one of my friends got up pee, and came back to find someone else sitting on his stool. He was told the rule is: Shuffle your feet, lose your seat.

It sounds more authoritative when it rhymes. It seems less likely that the speaker made it up on the spot. Therefore it's not just his opinion; it's part of folklore, so a lot of people must agree on it.

Moral: if you want to make up a rule, make it rhyme.

In this case, the guy who lost his seat took it with good humor. I still don't know whether it's a well-known proverb. I only heard it once.