Basically, punk rock is a style of music that typically prides itself on being against the mainstream and for being as DIY (do-it-yourself) as possible. Both of which this so-called "vintage punk leather jacket" go against.

The point of the leather jacket in punk is that you're supposed to customize it yourself, not buy an overpriced piece of crap like in the above picture. A lot of actual punk jackets end up looking like this: