They all come to the wilderness to get away of the stresses and pressure of everyday life. Most will enjoy meeting your Jack Russell Terriers on the trail, but some want to be left alone. This is especially true on long trails like the Appalachain Trail where solitude is King. So hook up your JRT's and give other hikers the respect that they deserve if they have a problem with your dogs. Then there are the Other People who show up at trailheads, and they are not so nice.
Trailheads attract psychos, drugheads and alcohol abusers, who have no thought of hiking.
They are there to party, break into your vehicle, rob you, or even kill you. We never carried fire arms until a psychotic gulf war vetern murdered a woman's husband, and then rape her before blowing his own head off with a hand gun just yard up from the trailhead at one of our favorite hiking areas. He had her husband kneel down with his hands behind his head, and then he shot him in the back of the head. We might be shot, but we're going down kicking and shooting. Everyday you read about damaged vehicles and robberies at trailheads.