Jim Dixon said, in part:

I do remember the custom of kids doing some kind of "trick" to get their "treat", but I think the custom was dying out because not everybody who gave out candy demanded a performance.

Since my alleged childhood (the Hallowe'en-relevant part, sixty-five to seventy-years ago) I have never understood Hallowe'en goodies to be a reward or payment for a performance.

"Trick or treat" is (or was in my kidhood) a variety of extortion. "I'm going to do some vandalism if you don't buy me off with candy!"

Dave Oesterreich