Reminds me of a ride with my son years ago. We were riding our tandem with a cluster of 5 single bike riders in southern Illinois. As we passed a farmhouse, a pack of 5 dogs came out to greet us. Each of the single bike riders grabbed for their weapon of choice - frame pump, water bottle, one woman had some kind of electronic ultra sonic thingie. I don't remember anybody using a loud horn or a chemical spray like Halt that day. My son and I didn't do anything. When it settled out, each of the single bike riders had a dog barking at their heels for a 1/4 mile or so. My son and I, who used no defense at all, were left alone.

I suspect that fear of dogs is the key factor. When we are afraid enough to feel that we need a weapon we must put out something that the dogs sense and find attractive. It could be that a new defensive system gives more confidence so you put out less of whatever it is that dogs sense.

Fortunately, dogs are much less of an issue than they have been in the past. I haven't found it necessary to carry any kind of defensive measure in decades. I'm riding a recumbent trike now so my face is right down at dog level. I hope that I'm right.