Granted, some folks prefer the "feel" of one line over another, but about half the folks fish with a single strand of non tapered flouro. As long as one stays within some fairly broad guidelines, they are going to be able to deliver a fly and catch fish.
THe appeal of tenkara for many is the simplicity, and being able to concentrate on fishing, not worrying about the equipment they are (or aren't) using. THere's certainly nothing wrong with tackle tinkering, if that's what folks enjoy. However there are people who shy away from fly fishing because they perceive it to be to complicated, and tenkara can offer those folks a much simplified and fun way to fish. That really was my only point.