A man and woman stand in front of a white building and look at their hands.
A husband and wife look at their hands
A man and woman are not assumed to be a husband and wife.
A man and a woman can stand together without being husband and wife.
A man and woman may be married or they may be single or they may be married to other people or one of them may be single and the other married to someone else so one may not be a husband and the other may not be a wife.