Why have two days of Yom Tov(Out of Israel)?-

One of the many reasons we have two days of Yom Tov, is because they made a decree that we should, because out of Israel the date of Chag was not known. So a question for today is why do we still keep this, we know the dates? So the answer is, which Posek is going to have the guts to get rid of such a day. So we don't get rid of it, and we still keep it.