Just a matter of safety. If they are supposed to be a certain birth year, then they should be . Maybe if these teams showed to an event such as Nationals, perhaps it would kill this argument . I know one parent (cousin) and her daughter is 13 months older than my daughter. That's why people care. It size , bone density and speed that makes all the difference in the world . If you think it doesn't , thats because you are probably violating it. But don't tell me they don't hold girls back because it happens .