Why Ethiopia has to absorb Eritrea or make sure it's governed by a puppet government !
For more than a century Eritrea has become a thorn in the flesh of Ethiopia being used as a stepping stone by historic enemies of Ethiopia such as Egypt, Arabs, Turkey and colonizers such as Italy. Italy may not had been able to invade Ethiopia with out it's foot hold Eritrea. Currently Eritrea is the hub of Egypt's activities to destabilize Ethiopia.