Actually, the phrase is etymologically significant. In the old, old days, 'man' meant person, male or female. It still means this in Modern German. 'Wife,' or wif simply meant 'woman.' At some point, man became more specifically used for 'male person,' but wif still meant 'woman' or 'female person.' So actually the term simply means 'man and woman.'
Of course, times have changed, and to untrained eyes and ears it appears that the case is that a man is still a man while a woman's identity changes. And in light of the change in the meaning of the word 'wife,' the phrase should probably be changed to 'man and woman.' This is the only way to retain the original meaning of the phrase. Using 'husband and wife' actually changes the meaning, and besides, 'husband' I guess can be perceived as a sexist term. Anyone who has any objection to using 'woman,' though has no idea where the word comes from.