I remember seeing this question in our Romans Study Guides but it had a different answer...
What do you suppose the answer was in the study guide?
Does not God then do injustice to man by requiring of him in His Law that which he cannot perform?
No, for God so made man that he could perform it, but man, through the instigation of the devil, by willful disobedience deprived himself and all his posterity of those divine gifts.
Heidelberg Catechism (Q9; 1563)