I think there's a lot of reasons. Initially, I think wood arrows are just easier to tune. Back then, wood likely meant cedar, and broadhead choices likely meant 125 grains or so, and the bows you bought were likely limited in variety as well. Now with the many different bows, arrow materials, and broadhead options, a little math needs to come in to play so that people can consistently shoot with accuracy all the different components that they choose to shoot.
Hunting ethics has evolved in the past 40-50 years as well. I read books by Hill, Thompson, Bear and the like, and the general consesus was to at least hit the animal. I think many people are trying for better odds than that now.
Sites like this are for traditional "fanatics", the population here, generally speaking, enjoys most every aspect of traditional archery. In the 70's it wasn't traditional archery, it was archery. The people here and other places like it love to tinker. To push the equipment and theirselves as far towards perfection as they can. With time, money, materials, options, and information comes a lot of opportunity to increase understanding and try new ideas, (likely new to the shooter, not the world of archery).
I shoot a Hill bow, with wood arrows, and a leather back quiver. Simple, right? The road hear took me through compounds, recurves, aluminum, carbon, bow quivers, high FOC, and a host of other "options". I'm grateful for the knowledge, the fun of learning and trying new things, and the mental roladex that will allow me to break out of ruts that are likely to happen. No purchase or test was a waste.
Lastly, I think the mentality of the "70's" is still around. Many folks keep it simple as well, and thats good too. That period and the guys who emulate that period serve as a point of origin for many new and different ways of experiencing archery.
I was listening to Ravi Zacharias explain to someone why there's so many denominations of Christianity, and it seems fitting here as well! :
"Unity of belief does not necessarily mean unity of expression."