Right, for motorcycle riding. The short cut keeps the jacket from riding up and the thick leather from bunching around your midsection or pushing up into your chin.
Know what the zipper on the sleeves is for? So that the sleeves can be zipped as tight as possible so nothing flies up them and so they don't roll up to your elbows in a crash.
And jackets with many zippers are for venting on hot days.
ANYWAY... that being said...
I think it's funny that some of you are digging on each other over questions and other such things about "taking part in an aesthetic" when it's all just based on copying something that had a real function.
IMO, If your leather jacket doesn't have thick leather and armor, it's just a fashion piece. And don't misunderstand me, there's NOTHING wrong with that, but when I think of it like that, it's kind of silly to dig on someone for being ignorant of how you're supposed to wear it or the manufacturing process or not knowing enough about artisinal whatever.
And that's just about all I have to say about that.
My riding jacket is a British Motorcycle Gear Montana. I LOVE this leather. Though it requires a lot of maintenance. Bugs and 70 mph winds and dirt, rain, etc dry leather out very fast. I've worn it every day during our 8 month riding season here.
There is just something about knowing that your leather jacket and armor might save your life or, literally, your skin that makes you bond with it in a way that just doesn't happen with the rest of my clothes.