You'd think the least they could do would be to just break the glass to get in.

If you put a flathead screwdriver between the window and door frame and twist, the window will often shatter cleanly and drop 90% of the glass inside the car, which makes it look less like he's trying to break in, as there won't be a pile of glass on the ground, just like the window's down. Either it didn't work or he didn't know what he was doing, resulting in a lot of damage to the car. Nice. So in addition to being a thief, he's also incompetent.