Why doesn't God speak audibly today?

I think the reason why God does not speak audibly to people today is because He has determined that the Gospel Message should be our main focus. We think that hearing directly from the Lord will make a difference, but He has already told us that the Bible is all the witness we need.The story of the Rich man and Lazarus proved this point. The rich man thought that having Lazarus return from the dead would shock some sense into his five lost brother. God told him that if they didn't listen to Moses and the prophets, a supernatural appearing would not change their hearts."Then he said, I pray thee therefore, father, that thou wouldest send him to my father's house: For I have five brethren; that he may testify unto them, lest they also come into this place of torment. Abraham saith unto him, They have Moses and the prophets; let them hear them. And he said, Nay, father Abraham: but if one went unto them from the dead, they will repent. And he said unto him, If they hear not Moses and the prophets, neither will they be persuaded, though one rose from the dead." (Luke 16:27-31)