Because Igbo's are proto-Bantu "forest people". Igbo's and other eastern Nigerians, Cameroonians, Congolese etc. usually have higher frequencies of lighter skinned people. They live in densely vegetated regions, i.e. Central African rainforest, therefore a decrease of lightsun exposure. Why would Senegambians who live in the desert be light skinned?
Don't blame the player, blame the game. It's a superficial, euro dominated world out there, so you have to think on the children. Give them a headstart, sort of.