I think Orion and others have explained this question well. I also started in the 60's. I knew a dozen or so other archers (all recurve shooters). All but two were older than me. For the most part we didn't know the draw weights each other shot (no forums back then). I wasn't aware of anyone shooting higher than low 50's. I was shooting mid-40's at age 16.
Frankly, among the guys I hunted with the archer's form, sharpness of broad heads, and shot choice decisions were considered more than the equipment the archer shot. We were also camouflage fanatics. Dull clothes, tree bark, or WWII or Nam tiger patterns, face paint, gloves, etc. I even remember spraying my Bear razor heads flat black except for the very edge.
Like Orion described when a bunch of folks switched to the compound one of the attractions was to bump up 10 pounds or more in max weight because of the let-off. In fact, some thought you should go higher in max draw weight to get a "clean" release with the let-off. Of course almost everyone shot with fingers back then (tabs and gloves). So, I went from 45# recurve to 60 pound compound so, at 33% let-off I'd still be around 40# at release.
As let-offs increased so did draw weights.
Then, I think just like Orion wrote, some compound guys started returning to recurves and kept up the draw weights.
I also think a few well known bowhunters, who also made bows, were shooting heavy draw weights and others followed.
Sadly, I think some have target related issues and can't get to full-draw. So, to get some performance out of their short draw they shoot heavy. Not everyone of course. Surely there are lots of heavy bow shooters (60#+) who have terrific form.
When you read about, know about, or have done it yourself-- put arrows completely throughs multiple whitetails with mid-40# draw weights, why punish yourself?
I keep a couple bows or sets of limbs actually, that will exceed (slightly) 50# at my real draw length of 26" just in case the moose dream comes true.