I know this is probably preaching to the choir, but I was just baffled by this issue.
I was walking my dog this morning and a lady drove up and asked if I had seen her husky that got loose. I said no and we each continued on our way.
2 blocks later, I see the dog. It was super friendly, came when I called, and was having a blast playing with my dog. Even better news, it was wearing a collar! Until I started looking at the collar closer and realized there were no tags or anything else with contact info for the owner.
I ended up deciding to start walking home, to see if it would follow us. Luckily a few houses later, someone recognized it and was going to call the owner. But, seriously, what if we had not come across someone who knew the dog?
Especially, for a breed that is infamous for running away. Why you wouldn’t pay a couple of bucks for a tag, when it could be life/death for the dog?
/End rant
You can buy them online, they’re not too expensive. I bought a more expensive one that has the detector at the end of along stick so I don’t have to get too close to an unknown animal. I carry it in my car in case I meet another stray I might be able to I’d their person.