I wore a leather bomber jacket in my 20s.
Leather coats were not a thing when I was growing up in Salt Lake City in the 60s and 70s. I never saw anyone of my father’s generation wear one. Certainly my father would not have spent that kind of money on a coat.
I started buying leather coats in college, and continued while I was in Japan. Now I’m in Taiwan, I never wear them anymore.
As an indicator of leather’s popularity back in the 70s, just about every mall in the Chicago area had a Berman’s Leathers - right next to the County Seat where you would buy your jeans.
For the past 20+ years my go-to jacket when temps are below 50 has been a VERY heavy down-filled leather bomber from Eddie Bauer. Just about getting worn in now! 
Maybe not in Rebel, but I’ve seen quite a few pics of JD wearing a leather jacket.
What I mean by mafia coat is the kind of leather coat you see mobsters wear in period scenes set in the 60s or 70s:
Those are leather car coats, referred to in post #9 above. Definitely different from the typical bomber/biker jackets
What the OP is probably referring to is the black leather jacket which is omnipresent in movies and TV shows about the 50’s. I remember the TV show “Happy Days” had a character name “Fonzi” (Arthur Fonzerelli) who was instantly recognizable as a no-count good-for-nothing biker-gang type because of his white t-shirt and black leather jacket. He always wore them with dungarees (you see kids, “Blue jeans” used to be called . . .).
It was a part of the show’s premise that Fonzi was actually a good guy, and even though he was good at fighting, he only did it for the right reasons. So everybody feared him, but his heart was in the right place.
In short, the black leather jacket was the replacement for the black cowboy hat in entertainment media. It was short-hand for bad guy. In practice, leather coat and jackets of various sorts were worn by all sorts of people, but black leather was mostly worn by motorcycle aficionados, who valued the protective qualities of leather.
Dad didn’t wear leather jackets that I know of, but as a teen (late 50s/early 60s) he wore jeans/white T-shirt/loafers which seems sort of greaser to me. I have a heavy leather jacket I bought 30 years ago which goes in and out of rotation–it’s a Nehru collar biker jacket. I’m not a biker but I was into punk, and a lot of my punk friends had short leather “biker” jackets, though usually the wing-collared style.
I am not old enough to answer from experience, but I remember hearing that as late as the mid-70s, Fonzie caused something of a scandal among Happy Days producers by wearing leather, and they started him off wearing a brown leather jacket to soften the blow because black was too scary, I guess. Early on, he actually had a windbreaker, and was only allowed to be shown wearing a leather jacket when he was near his motorcycle. Leather was still associated with criminals and thugs. Which might make sense for the Mafia, but the mob often liked to dress like legitimate businessmen rather than crooks. And a conservative, middle aged man probably wouldn’t have worn one at the time, no matter his job.
In the 90s I had a black leather biker jacket with all the hardware. It was a sweet albeit costly jacket. I took it to the store where I’d purchased it to get a small tear in a pocket lining repaired. I had my 6 year old son with me, and he was admiring all the coats while I waited in line.
A saleswoman approached my son and began chatting to him about jackets. He told her he was going to get one when he grew up. “Why wait?” she asked and walked him to a corner of the store where they had little biker jackets for kids. Meanwhile I was stuck talking about my pocket tear.
I ended up buying him one. Our “in joke” was that he would take other kids’ lunch money to pay me back. He wore that coat every day for about 6 months, then a growth spurt made it useless.
My grandfather, born 1903 and of mostly German ancestry, frequently wore one. This was in a mostly Irish-Italian neighborhood neighborhood in the Bronx. (My grandmother was Irish-American. In photos from the 1930s and 1940s some of his friends also had leather jackets.
I can’t recall my father wearing one but he wasn’t much for style. But it wouldn’t have been out of place for guys in his generation (born 1920s).
I don’t remember seeing any pictures of my father (b. 1939) with a leather jacket, but he was more of a jock in high school, had cool cars and then joined the Navy.
My uncle (b. 1942) was a greaser in high school, road a motorcycle and wore a leather jacket.
Just reading the topic, I thought that’d be an awfully large jacket.