Why do people use help dogs?

i have a dog that falls into the help dog category but only at times. I have a really rough blue lacy that when i have my main strike dogs on the ground he will stay close to me/the truck and will honor a bay and he either bays super tight or will catch if he feels like it. However, if i am running a long night or one of my strike dogs get hurt he seems to know when they are not on the ground and will go out and hunt and strike just as well as my best strike dogs. Its seems like he knows he can depend on them when they are on the ground hunting, but he also knows that when they are not hunting he has to do it himself. He is a help dog as far as i am concerned but i can't get rid of him for the simple fact of if my others get hurt or cut up i will have nothing and he can fill the spot no problem.