Well, this is a touchy subject that comes up here often. It is kind of like why some christians do not believe some teaching in the bible because they think that society today has a much more sophisticated answer. Sexual morality and what society thinks is OK is just one example.
 
We know that there will be deception in the last days and dreams and visions are certainly an avenue for that. However God has specifically said that his people will have dreams and visions. God has used these methods of relaying information to his people from the very beginning. If it is from God it will confirm what the word says and it will pan out eventually.
 
We all are given certain gifts, we should not doubt this gift just because we do not have it. God has always had his gift of prophesying to his people in this way so do not be so quick to scoff but examine your own heart and make room for the others gifts. Like Red Green says, "We are all in this together."