Leaving the bowl out goes back to at least the 50s, sometimes the homeowner goes to bed early, or something comes up, or they are having drinks and a little party and get into their inside grown-up party and lose interest in the door.
In the 50s leaving some of your own candy in an empty bowl would have been a fairly common reaction, conditioning children is an accumulation of 1000s of messages and in the 50s the positive behavior messages were constantly repeated in every way and in everything, and every day, everything you read, everything you watched, everything that was said to you was always, be good, be thoughtful, be helpful, be humble and honest, help little old ladies, stick up for what is right, God is watching, be nice.
In the 50s leaving some of your own candy in an empty bowl would have been a fairly common reaction, conditioning children is an accumulation of 1000s of messages and in the 50s the positive behavior messages were constantly repeated in every way and in everything, and every day, everything you read, everything you watched, everything that was said to you was always, be good, be thoughtful, be helpful, be humble and honest, help little old ladies, stick up for what is right,
In other words, don’t be a Mr. Bungle
https://www.youtube.com/watch?v=oD9iL1iRb8A
“Big enough cake, or what?!?!”