Maybe because a gang can be more of a family than someone's actual family in certain situations which it is very important for people to take family serious instead of just being related to individuals. Different circumstances for different people does not allow for a perfect black and white world where every shape fits in a perfect hole for the shape as there are no perfect holes in life. Life is not a simple A+B=C formula. Variables always throw off the equation.
There could be, I can't personally do the count but I have seen enough in my travels in life. Hell, some kids don't even have "homes" to call "bad".