Address data not being used from registration step

It was my understanding that the address from user registration is automatically used in the billing address. Now, when I test buying something, I register with an address at step 1, but the billing address step is empty and requests the user to create one.

My checkout workflow is cart,login,address_shipping,payment,confirm_cart_status_fields,end

Any idea why this might have happend?

I have just realised that this only happens when a product is free.

This isn't an issue since we won't be offering free products. So I no longer need an answer to this thread.

Not sure why it happens though.