Why all the casual beatings & fistfights between friends in pre-60's movies & stories?

In reading a lot of Heinlein and similar science fiction or viewing 30’s 60’s action movies friends and acquaintances were always physically assaulting each other over minor differences in opinion or for manners oversights. Fistfights were practically a requirement for male bonding.

I’m 56 and I don’t recall people beating the shit out of each other on a regular basis growing up in the 60’s & 70’s. Kids did get spanked and switched but full on fistfights or physical assault at the drop of a hat were rare.

When did all this fighting between friends stop and why?

It’s simply a dramatic device used to inject action into what would otherwise be a dull disagreement over minor differences in opinion or manners oversights.

Similar to old westerns where there were a lot of scenes of people riding horses, even though there wasn’t actually anything in the scene that moved the story.

I’m a little older than you and we did have some of that; mostly as kids but some as adults. But not nearly to the level Hollywood portrayed. In our case I always wrote it off to being really rural and basically a year-long version of “cabin fever”. After seeing each other every day for years, even your best friend could become a raw nerve you just needed to hit a good one; of course you knew he was going to hit back. It was never at the drop of a hat; it simmered its way to the surface. But it happened sometimes.

There is still some of that but it basically died down and finally mostly out during/after the 80s and and into the 90s. You almost never work with the same few people for year after year the way you used to and people move in and out more even back in the mountains. So some of the pressure that caused it is gone.

Happens with kids still sometimes. Not that much with adults and not much in bigger cities.

In movies from back in the 30s and 40s, people were always slapping each other (especially a man slapping a woman) or threatening to give each other “a punch in the nose”. Or how about the Three Stooges?

And IRL, when I was a kid in the 50s, there was a classmate who beat kids up on a daily basis. His father taught him to fight, and he did it with no provocation. I don’t recall anyone ever stopping him.

According to my father, my uncle’s best friend in grade school was the one boy in his grade that he could not beat up.

A lot of people took the attitude that fighting was the natural way for young males to vent their energy and establish their places in the social order. Officially, it was forbidden, but as long as no one was killed or maimed, authorities often looked the other way.

Death duels were officially illegal, but often socially accepted, up until the Civil War. The “boys will be boys” attitude to fisticuffs was fairly common until World War II.

In my opinion, it became less acceptable in the 1950s and 1960s, when parents started worrying that Those Other People might be carrying weapons, and their own innocent darlings might get killed.

Perhaps their wives weren’t giving them enough.

It’s amusing that the OP mentions Heinlein. Engineers had a much more rough-and-tumble, ass-kicking image back in the '50s than they do today.

Quoted for truth. Engineers were the guys who went out into the boondocks to build hydro-electric dams. Engineers were the boffins who gave us the tools to lay down a world of hurt on those damn Nazis. Engineers were badasses.