That is one of those mysterious questions we players have been asking since we noticed this that never get any legit answers to, so apparently we'll never know, and the ones with the answers like to keep it to themselves. But I agree - it is ridiculous all costumes are not available for Halloween as they should be. Other wise what is their point? I just never try Spooky Day any more and delete it off the calendar. Bad enough our Sims kids can't go Trick or Treating - they and the other Sims can't choose any costume they want either, so in my mind that Holiday is broken and does not exist.
