Hamlet and Oedipus Love

I just realized that in the play Hamlet and Oedipus both main characters falls in love with their mother. However in Oedipus' situation, I do not blame him for sleeping with his mother because he did not know. He was left to be killed by his parents so they can save their own lives. Hamlet however, I can't believe he was developing feelings for his mother especially the fact that she is your mother, he knew about it, and why would you do that if you seen your father's ghost. I guess I some what understand why they fell in love with their mother because she is the one you feel most comfortable with and they are the ones that take care of you but I think that is disgusting. I don't know why in the past, this was not seen as taboo because there were lots of kings, queens, princes, and princesses having incest to make their blood line pure. Now a day, since we know the complications of incest so maybe that is the reason why now it is consider taboo. I'm sure if the past new about the diseases that comes with incest, they would not do it.