Monopods are, for me, an essential part of photography, especially where longer lenses and shutter/aperture demands translate to stability.
I always pack one in my checked luggage when on a photo trip - especially overseas or in rugged areas. A good, sturdy, monopod is also a valuable aid as a hiking stick in some rough areas.
You see sports photogs using them because of having to always be ready to shoot the action. Holding a DSLR and lens in the ready position for extended periods of time would really be tiring.
So, they sit and let the monopod carry the load. The added stability makes their use a no brainer.
For panoramic, it creates a very good pivot point.
Also, note how many of them are white lenses - Canon rules with pro sports photogs.