I imagine that alot of people dont understand and/or have the knowledge need to be able to put together a setupwithout at least some tinkering to get it right, but in my case its more or less curiousity, and the enjoyment of tinkering, I guess you could even call it a hobby
I agree that if you know the basics of arrow setup that it really shouldnt take that long to put a setup together that works good, and I agree with the point of "dont fix what isnt broke" and in general I dont, but I personally like to tinker beyond what is presently working, just to see... but until(or if)I find something that works better, I always stickwith whats working at the time...
I'm the same way with loads for my firearms, I have a load worked up for my .270 that gives me consistant 3/4" groups at 100yards, thats beyond excepable for a hunting round, and thats what I use, but I still play around with different components, just to see if I can maybe come up with a little better...
I have a target hanging on my wall with an 1 1/4" group that I shot at 400yards with my 22-250 too and some would say that with that kind of accuracy there isnt any reason to work up any more loads for it, but I still mess around with that round too(with a different set of dies, I aint messing with my "good" setup

)... and again,itsnothing more than for the enjoyment of doing it
I will saythough that once I get a bow or gun setup that I very rarely ever mess with that setup again unless I find a better arrow or load combination that requires it, although I do make changes here and there my experimenting usually always envolves the projectile, not the weapon
I'm pretty much the same way with everything I do, I have to know how everything works and I'm always looking at ways to imporve and/or modify things...
youd be hard pressed to find a machine in my garage that hasnt been messed with and has at least ONE modification done to it