That was my first thought as well.
Darker skin in colder climates is also a benefit because the glare of the snow may introduce unwanted amounts of UV rays to the body, even more so than summertime. However, it might have to do more with the baggy clothes that are worn in the summertime combined with the lack of nutrition that many of these youths have. You’d be surprised at how many black youths turn their noses up at nutritious foods.