This question has been already asked several times it is better you close this thread if you got the answer you want.All i got to say to you is that you cannot directly use btc to buy whatever you want as it is still not popular for most of the trader and you will have to convert them to cash to use them so it is a silly question to ask whether we need btc or USD because we all need the fiat currency so that we can buy what ever we want.