Hi, rachellelunaa!!
I think the reason we have so many bones is because, firstly, the cranium is such a unique shape that we need multiple bones to form it. Also, another reason we are born with separate cranial bones is that when a baby is born, there is an incredible amount of pressure being administered to the baby during the process. The many unfused bones allow the child's head to be malleable, and therefore preventing damage to the skull and brain. As we grow, we no longer need these bones to be malleable and they fuse together.
I really hope this answers your question!!
