There are a few important reasons to use a net when fly fishing. The first reason is that most fly fishers catch-and-release the fish they catch. A good net is safer for the fish because it lets you land the fish before the fish gets too tired. If you wait until the fish is too exhausted to move, the build up of lactic acid in the fish can become lethal. For beginner fishers, a net also lets you handle the fish in the water without squeezing it, which also lets you more quickly and easily remove hooks. A rubbery net material helps keep the protective slime on a fish. Those are the benefits to the fish. To an angler, a net will help you successfully land more fish — and maybe even land the fish of a lifetime. Lots of winning with nets.
To learn more, check out my guide to the best fly fishing nets at Man Makes Fire.