Nikki (Marie Avgeropoulos), a lovely lass in a hoody, falls off a car she's jumping on and lands on Cam and crushes his bike. It's love at first pileup, and our hero soon joins Nikki's crew of parkour aficionados who are criminals for hire.
I would assume that parkour is helpful if one happens to be in a situation where they need to quickly escape from vicious dogs and the only way out is jumping over a super tall wall. For regular folks it definitely strengthens your core, arms, legs and butt.
Now that people are learning new things faster, and recording what they are doing, it challenges others to do something more advanced, in other words, "one-upping" and that ultimately continues the trend.