I understand that modern outer layers are more functional. A leather jacket, for example, can be dressed up or down so as to be worn in a variety of situations. It is also better at keeping you warm.
However, I think capes/cloaks are more aesthetically pleasing garments. It also feels good to have the fabric flowing around you as you walk. But what do you think?
The other big reason is that the world is cleaner. Capes and cloaks also protect the whole body from mud/dust and can be easily removed. Riding a horse or walking on dirt roads is a lot dirtier than riding in cars or walking on a sidewalk
The original type of coat that would have been worn when riding was the Great Coat - which did cover the whole body, down to the ankles (and included the front of the body much better than a cloak). Those would have been worn by military officers, particularly.
Those were fine for riding, but then if you were off your horse and end up in the newly developed trench warfare - starting from around the US civil war onwards - you ended up wading through mud which got caked to the coat. So then they started cutting the coats shorter and they became Trench Coats.
I WOULD LIKE TO SUBSCRIBE TO COAT AND CAPE FACTS
Horse shit. In cities, you waded through horse shit.
As someone who has done extensive reenactment in period dress, sometimes in towns dedicated to realism that banned cars and relied on horses for travel, you wouldn’t believe how terrible even a dozen carriages and a few dozen private horses can be to your skirts/trousers and shoes. Especially when it rains.
People sometimes make light of women in the past who changed their outer clothes two or three times a day, but if you were in town, your attire would be absolutely foul after a few hours in the same outer skirt. A long cloak helped immensely to keep your skirts or trousers from soaking up horse sewage.
Once cars took over, that stopped being a problem, cloaks weren’t as desirable as they obscured fashion, and coats became shorter and more for protection from the weather than from horse shit.
There was a bit of military influence, but that was more about fashion than functional influence.
e: clarification