This question and answer naturally reminded me of a fine Stephen Jay Gould essay that expands on the same topic, as well as some similar ideas. Called “Male Nipples and Clitoral Ripples,” it explains that Gould often gets the same question: Why do men have nipples? People go to great lengths to figure out the evolutionary advantage. The answer is that evolution is more complex than that. Indeed, men get no advantage from nipples. However, men and women are cut from the same cloth. Just as the clitoris and penis develop from the same tissue, male nipples are a developmental artifact of the same tissue that leads to female nipples (whose value has never been doubted.)
Here’s the essay in full:
ETA: Link to Column: Why do men have nipples? - The Straight Dope