Because in many areas, stronger sprays are prohibited by law. The people who approve those laws are not the ones out there having to deal with problem dogs!

Having been issued Halt! by the USPS, I can objectively say that it is next to worthless, maybe even worse than not carrying it at all. I had a can with me in my car/truck because I was required to have it, but I never used it on a dog in 33 years. I was never bitten by a dog I saw first. The four that did get me all snuck up from behind, so Halt! would have not done any good.

If you have ever discharged that can in the past, or if the can was exposed to high temperature, the seal will leak all pressure over the course of a few weeks. So the next time you need it, it will not work! This is the same sort of issue there is with a dry-chemical fire extinguisher - once used they should be recharged -- but at least an extinguisher has a pressure gauge! Halt! doesn't.

Halt! shoots a pencil stream, maybe 10' on a good day in a no-wind situation. Oh, and to be effective, you must get that weak pencil stream of mild taco sauce in the target's eyes and nose. Have you ever tried to actually hit a moving target with a pencil stream? Did you check the wind direction and speed first?

Ask hikers what they carry in bear country. It isn't Halt!, nor is Halt! even recommended. Halt is barely 1Million Scoville units. They recommend a more powerful spray fog!

As for me? When I'm riding, I carry the most powerful (Fox 5.3 cone fog - 5.3Million Scoville units) because I do not stop, I'm moving! The fog spray shot behind me - where the dog will likely be - it will get some in the face. The Fox spray also contains a UV dye so if you do want to file a complaint afterwards (not sticking around at the scene to incur the wrath of Ol' Bubba for spraying his dog), the dog will have the dye marker on it. Makes for a better 'case'.