Why do we only start counting Kings and Queens of England from after the Norman Conquest?
Because its all part of the unspoken conspiracy, started at the time of the Norman Conquest and perpetuated to this day, that there is no English/British history between the time the Romans left and 1066. Even at the time of the Queens 80th birthday it was said that she could trace her lineage back to William I, nothing being said about the earlier monarchs.