Because Neanderthals are not human! They are archaic! At best, they can be thought of as a remnant species of sub-species Homo Rhodesiensis (heidelbergensis) that never evolved into Homo Sapien! All the rest of the Homo Rhodesiensis (heidelbergensis) were wiped out of Europe and Asia by the Homo Sapiens. At the least, Sapiens are Homo Erectus still walking the earth unchanged for 500,000 years!