Because you're a pathetic, sedentary chump.
Not much else to say here, really, other than that I immediately recognized this as my native Chicago, where even the amateur parkour scene just seems to be on an entirely other level. I can remember packs of extreme bros making minced meat out of my undergrad campus, all barrel-rolling and gainering and whatever else they do.
Also, more people who get a kick out of tempting extreme bodily harm (death) need to start rigging themselves with FPV/POV cameras so that I can continue living vicariously through your life-affirming feats of agility and strength and your complete disregard for your person.
Per usual, you'll probably want to put this one on mute.
Reach Brian at email@example.com. @thebanderson