I looked around myself at the age of 10 and realized I was too old for Trick-or-Treating. In fact, the idea of doing it suddenly seemed kind of childish and embarrassing.
I still love all the Halloween and horror accoutrements and nomenclature (toys and decorations), but even back then (in the 1970s) it was obvious that the only kids still going door-to-door at the age of 10-12 or older, were mostly bullies, horning in on what was really a little kids game. In this day and age, when even 12 year olds can be aggressive gangbangers, it certainly looks pushy and suspicious for them to be out on the streets, elbowing their way through the little kids and their parents, for candy they can easily afford to buy for themselves.
By the time you're a teenager, there are other things to do, like Costume Parties, Haunted Houses (either attending, or helping to build or staff one), or just staying home and passing the torch by handing out treats to younger kids.
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"I don't mean to sound bitter, cynical or cruel - but I am, so that's how it comes out." - Bill Hicks