I am often asked “why should I learn scales [or other such seemingly-nonsensical things] on the banjo?” The ultimate answer has finally occurred to me;“wax on, wax off” (from the first Karate Kid movie–if for some reason you are not familiar with that phrase. . .actually, how could that possibly be?).
If you want to learn and improve, you should learn and practice the things you are not yet capable of (or in the case of scales, the things that will make you more capable), regardless of whether you think you “need” them or not. If you want to stay the same as you are, then continue doing what you’ve been doing (or, not doing) and be content in your complacency. This of course applies to anything worth doing well.
I am not a cheerleader for the four-string banjo status quo; I am an agitator for what could be.
That is all.