Special teams are a very important part of football. They make the difference as to whether or not Cleophus Jackson is going to "take it to da house" on a kick return. My opinion as to why we are so common on special teams, is that there is a lot of field to cover and a lot of responsibility involved. Plus, a lot of guys are only used for this specific duty, which means that this is what they train for, and nothing else. Think about it, these guys make the difference as to whether or not the return man is going to go down at his own 20 yard line, or YOUR own 20 yard line.
Plus, it gives caste-following coaches an excuse when they are approached about why they don't have any Whites at certain positions. They can turn around and say, "Yes I do, look, there they are".