Trick or Treating In London, England
Halloween is very unEnglish idea, the lack of a real local "community" means the idea of knocking on stranger's door and asking for sweets (candy) or money(!) is looked down upon.
Of course the sheer hideousness of British teenagers can turn Halloween into a dreaded night, as they come along, not in fancy dress, and mumble "Trick or Treat" and then proceed to turn your front door into an omlette if you don't satisfy them financially - more or less a protection racket.
Also it's accused of scaring old people - who have no idea of what halloween is - to death, the fact it's an evening of "begging", the dangers to independent children, etc, etc all combine to make parents pray their own children never want to go trick or treat.
The real problem is however British children watch more American cartoons than anything else, and American cartoons advertise the Apple Pie image to British children very well so that Halloween means fun, TONS of sweets and non-stop slightly scary adventure.
Then they ask their parents :
British Child - Mummy it's halloween today, I wanna go trick and treating?
British parent - It's Hallo-what? Hallo? Ween? Oh no that's an American thing dear, we don't do that.
Child - Noooo! All my cartoons were showing trick or treat, and I wanna do it!!!!!
Parent - Look, they were American cartoons, we don't knock on doors for no reason in England, it will scare the old people and it's dangerous and it's begging and...
Child - *on the verge of major tantrum* I WANT TO GO TRICK OR TREATING!!!!
Parent - *cursing the cartoons* Damn, okay, then WE can go to ONE house - (*usually a relative) - and do ONE trick or treat, okay?
Child - *sniffles* Okay!
Parent - Now, go and dress up as some kind of bloody goblin you got five minutes, and hurry up!!! My soap is on in 20 minutes. *checks watch*
The child then proceeds to put some ragbag costume on, and the parents phones up the relative/close friend they're going to knock for, to forewarn them to have some sweets ready.
Then the said child is rushed over to knock on the said door, say "trick or treat" and gets given some mediocre sweets and leaves with his dreams of an American cartoon-like Halloween thoroughly crushed.
N.B. Most British parents save up their bonhomie for Bonfire Night which is a much more enjoyably British affair - torturing and burning Catholics + fireworks.