I personally don't have experience with this, but I've known people who refused to put collars on their indoor cats because they think they are well behaved and won't escape. Then, when they do get outside somehow, they aren't found unless something bad has happened to them. It's just much harder to find lost cats than dogs. If you see a nice dog walking around, it is almost certainly lost, and you can contact an animal shelter or vet or something. If you see a nice cat walking around, it could be lost, or it could just be an outdoors cat. So moral of the story is, collar and tag your pets, even if they don't like it. It's like eating your vegetables as a kid. You may not like it, but it's for your own good