An ex-girlfriend if mine was a nurse at the local hospital.
I went up there too take her to lunch one day.
It seemed like every nurse/doctor was wearing a pair of them.
My lady friend said they were popular because assorted " bodily fluids" washed off easily :P

A friend of mine has a Podiatrist as a brother-in-law. he loves the Crocs and the Flip-Flops!  Seems his business has increased in direct proportion too there popularity. Lack of proper arch support is the main problem. But, like the ladies pointed toed /stiletto heel shoes, style trumps practicality and foot health every time ;)