If you have outdoor/feral cats that won't come in I understand (I have one too), but if you can keep your cat indoors, I would strongly recommend it (especially in cities). My little feral would never go up to a stranger and is very cautious about dogs, etc.
Too many horrible things can happen to outdoor kitties. Cars on the road, dogs, cruel people
, other cats & disease, poisons, etc..
Also, cats will crawl up under car engines in the winter to keep warm (bang on your hood in the winter before you start your car, in case a neighborhood cat is hiding in there!).