The force of love, guilt, shame, etc. are much stronger and more common than akrasia. It is rare for humans to want and to be able to disregard these feelings completely in the long run. I don't think akrasia functions as a social adaptation - these feelings are themselves the adaptation.

Not to mention the fact that by far most cases of akrasia hurt your social lfe: akrasia can prevent you from making new friends or meeting existing ones or indeed from doing anything at all, in the worst cases.