YOU SAID:
Why should you do this
INTO JAPANESE
なぜあなたはこれをする必要があります
BACK INTO ENGLISH
Why you need to do this
INTO JAPANESE
なぜあなたはこれをする必要があるのですか
BACK INTO ENGLISH
Why do you need to do this
INTO JAPANESE
なぜあなたはこれをする必要があるのですか
BACK INTO ENGLISH
Why do you need to do this
That didn't even make that much sense in English.