I have a large, heavy Kirk ball head on my monopod. The reason is simple...there are times that I can't angle the monopod to the angle I desire the camera to be at for framing the photograph. Some may consider that a left-right only swivel is sufficient for a monopod, but I still get myself in situations that for stability, the monopod is at an angle to the floor in front of me or even backward slanted through my legs, and I have the camera either horizontal or somewhat tilted slightly upward to capture players on a stage. The ball head gives me unlimited angle opportunity.
So, even though I have a cheapo monopod, it does the job intended, has unlimited angular capabilities with a ballhead, could be used as a walking stick with a ballhead handle, and makes a terrific weapon should the need ever arise. However, in crowded rooms where I normally use it, moving from place to place to get the next shot with the monopod extended more than 24" give or take is hazardous to everyone within my trip & fall range.