A trend either worn by: a- celebrities such as LL Cool J back in the early 90's or Eminem, b- the thug or gangsterish crowd, c- people who ride bikes.
Situation: Adam had "one pant leg rolled up" accidentally. Melissa gives him an awkward look. He says, "Yes I'm gangsta!" She replies, "You know who else wears their pants that way?... People who ride bikes!"