I agree with your basic premise and found myself thinking the same thing at first. Then after playing for a while I'd get in the zone where I could go for long stretches w/o dying, that there was a certain logic in the layout. I ended up having a lot of fun playing it and wished it was longer. The atmosphere was well done, too. Also, I tried it with a gamepad at first and found the mouse/keyboard is WAAAY better, as usual, so perhaps that didn't help console sales.
A few year ago a tried parkour around the Boston area and found it a lot of fun and very challenging. I stopped quickly after a) being terrible at it and b) breaking my toe. But, the people I did meet and watched had a philosophy which I think was captured very well in this game. That being said, I can imagine why video game that intends to appeal to people who are interested in parkour didn't sell well. They're too busy doing crazy stuff at your local T-stop.