You may ask, “why does simplicity matter?”
Simplicity matters because it is liberating and makes fly-fishing accessible and intuitive. Take, for example, the idea that tenkara anglers in Japan use only one fly pattern, and don’t change it. It goes completely against the thinking of western fly fishing, where, if the fly pattern is not working, it should be changed.  And fly fishing requires dozens of fly patterns, and a hatch-guide book must be consulted before going fishing. Tenkara’s focus on technique rather than gear means you can go to any stream in the world in search of trout without worrying about what flies to take. This philosophy of not relying on unnecessary gear applies to a lot of things people may tell you that you need to fish, from leaving the reel behind, to not needing leaders, to realizing split-shot, strike indicators, floatant (the list goes on), are not needed to fly-fish. Liberating.
The small amount of equipment and speedy setup means we can take tenkara anywhere and enjoy it with other activities. Going for a hike? Bring tenkara along (and just one fly pattern). Going backpacking, climbing, canoeing, foraging? Take a tenkara rod, line and fly and enjoy fishing along the way. Read about TENKARA+, the idea of enjoying tenkara with anything.