It's quite simple really, Dragapult physical attacking movepool isn't quite impressive. With its special attacking movepool, it has access to water, fire and electric coverage. It also doesn't have that good of a physical stab for ghost type. The best it can do is phantom force which is incredibly easy to play around. The lack of a goood ghost stab is what really lets the physical sets down
Also, while spa Dragapult is the more common, dd Pult is also used mostly on hyper offense teams with weakness polcciy and behind dual screens so that phantom force won't be too much of a problem
