This is a true story: it happened to me...
We had some friends over for a weekend. Roast Beef for supper (hmmmmm). My wife prepared the roast (a little seasoning, some garlic, and so on) and dropped it into the pan with some onions and potatoes. My buddy & I sat back making sure the wine didn't evaporate, when his wife pipes up "Aren't you going to cut the end off?"
"Huh?", we all asked. (I stress: all.)
"Oh yeah, sure, you're 'supposed' top cut the end off."
"And do what with the piece you cut off?"
"Toss it out."
After about 15 minutes 'discussion' around this point we all convinced Laura (my friend's wife) that shoe ought to trust that "this will be OK".
Of course, the roast was fine (and the 2nd bottle of wine didn't evaporate, either).
Later we all got curious and asked why Laura thought that the end of the roast needed to be cut off and tossed. "That's the way my mother taught me." We all convinced her to ask her mom about it, next time she went visiting.
So she did, and her response was "that's the way my mother taught me." So of course they headed over to the nursing home to see Granny.
These two are standing in front of Granny asking why it's so important that the end of the roast be cut off. These two misunderatood the stunned look on Granny's face and began explainign it all over again when she interrupted. "You two! Weren't you paying attention. In those days, the butcher cut a roast 'this long'", motioning with her hands, "but the pan we had was only 'this long'". Of course, her hands were a bit closer together. "So I had to chop the end off. Hell, the dog loved it!"
In other words: That's the way we have always done it around here.