Leather coats are masculine; it’s just that simple.
Tough guys have worn them since the beginnings of human history, back when the best source for a leather jacket was something you’d killed and skinned yourself.
These days you don’t have to be quite that intense to get your hands on a good coat, of course. But the image is still there, along with the cultural memory of countless tough guys doing tough things, on film and in person.
Even a very smooth and polished leather look has those same primitive associations with toughness, hunting, and swagger. It’s all the intensity of spikes and studs, without the flashiness or pretense.