Zoom lenses are great. They are flexible, quick to respond when you need different focal lengths in a hurry and generally light to carry.
They do have drawbacks. Unless you invest in wide aperture zooms which are both expensive and bulky you can struggle when the light is scarce and you need a short depth of field and a long lens. Of course, you can bring up the ISO, but above ISO400 the grain starts to build and image quality degrades.
Those of you who have shot in the souks of Marrakech will know the variability of the light and how when you see an incredible image it is always just where the light levels are weakest. The shot you here was exactly those conditions. The portrait needed a fast response and I wanted 200ml focal length so as not to disturb my subject as well as a f2.8wide aperture to create tight depth of field.
I used a 200ml f2.8 prime telephoto lens a to capture the subject, whose pose and position in the souk light made it an ideal full-length portrait. I would have struggled and had to make compromises with a zoom. Yes, prime lenses are inconvenient, slow to swap out and overall expensive when you need several. But just sometimes they can make the difference between getting the shot you want and getting something you just feel does not justify the potential of the moment.