I take a leash, but only used it when needed. Our dog is very well trained and gets daily practice on not chasing animals. Our daily walks, even though in town, often encounter sqirrels, deer or wild turkeys. She will 100% follow a "lie down" command at distance. It took hundreds of hours of training to get our dog to the point she is now. And it takes repeated reinforcement.
On trails, we have the dog move off the trail and "lie down" if someone passes from the other direction. Our dog is a border collie, and as a herding dog, she thinks her job is to herd us, so does not leave our side. I have had to put her on the leash when I fly fish after 4PM, because she loves to swim, and I do not want a wet dog in the tent at night.
Unless you walk easy, flat trails, it is hard for a dog to walk on a leash without stressing their paws. Dogs do not naturally go up over a rocky section of trail the same speed or method we do. If the result is that the dog pulls on the leash, it is very hard on paws.
As for bears and such, we had a bear walk right by our camp and our dog just sat there looking at us, not making a move or bark. We just said "sit". We did put the leash on her then, just in case the bear charged. We did not want her to "defend" us.