This is another way to focus our skills (really, no pun intended) and make us work just a little harder. A trip out somewhwere, and just one lens. Now we could cheat and choose something like an 18-400mm, or we could get into the spirit of things and choose a prime lens. For a real challenge, choosing an oddball lens such as a fisheye adds a bit more challenge to the situation. Also, perhaps choosing to take a lens that is totally unsuitable for the situation, at least at first glance. A 200mm lens in a museum? A 50mm macro lens for shooting birds in flight? Of course nothing is impossible, just more or less challenging.
I actually do this quite often, in the context of doing lens reviews for EPZ, where I do go out with just one lens, but I do try to choose locations that will result in some meaningful shots.Let's see now what I shot with the Samyang AF 85mm f/1.4 RF.
Actually, the one lens concept can be very liberating, travelling light, no decisions as to which lens to use, just pure photography with no distractions. What's not to like?