I haven't owned garb since college, though I'll be getting back to it reasonably soon now. I also don't celebrate Hallowe'en or Samhain. I do celebrate Purim, though, and I would totally wear SCA garb for Purim. It would stop me from having to spend money on a separate costume, or spend time and effort doing something which is very difficult and unpleasant for me (sewing), and I'd look fantastic.