This feature is broken.....I have actually reported it on the HQ forums and provided a save....hopefully they made something out of it. It seems almost no one is getting trick or treaters spawning.
As for the trick or treat interaction IT IS in the game. It was actually even patched with a holiday event back in the day so they have the code for it, and sims are suppose to actually animate and give a little candy to others. Tricking is just the scare interaction recycled....lol If you threw a Spooky Party you used to be able to use these interactions but they no longer appeared after Seasons. In the same post I did talk about the missing trick or treat interaction so maybe it's looked into, but knowing how this game operates it'll be a year before they fix it if at all.
https://answers.ea.com/t5/Bug-Reports/NEEDS-INPUT-S-No-Trick-or-Treating-during-holiday/m-p/8284552#M106936
You'd think though that with Seasons they'd make trick or treating more intricate and add new animations but nope.........