How Did Dance Tutus Become Runner Chic?

I’ve run a handful of races per year since my first 5K in 2008, and have done enough theme/costume runs to be used to seeing women (and occasionally men) in fluffy statement skirts—sometimes stiff ballet-inspired tutus, sometimes just sparkly costume skirts (utilitarian running skirts are a different sartorial category.) I stopped thinking of running tutus as a novelty, however, when I saw them being sold as official merchandise at the 2013 Color Run in Chicago.