Because the phrase ‘by the penny’ is implied that whatever it is, will squeeze all the value out down to the singular digit, because the penny has a value of 1 cent as we all know. However, with the penny no longer in production, how soon can we expect a time where nobody will say “by the penny”?
How long did it take before references to ha’penny (pronounced haypenny, short for half penny) stopped after those were phased out?
There’s a song I know of that mentions them and that’s it. They were in use starting in 1672 and phased out in the 1970s, so a hugely long time, yet they are never mentioned anymore despite being in use during modern lifetimes.
Perhaps people from the UK hear the word more often, but I basically never come across it in media or anything, even period pieces.
(The song I know is “Christmas is coming, the goose is getting fat, please to put a penny in an old man’s hat. If you haven’t got a penny, a ha’penny will do, if you haven’t got a ha’penny, than god bless you”)