Why do men have nipples?

Answer 1

Because hormones in the fetus determine whether you are male or female AFTER the mammary glands begin to form.

If you are going to be male, the mammary glands fail to completely form due to their exposure to testosterone produced by the forming male genitalia.

Answer 2

As cells in the mother's womb we all start out the same. As we develop, the sex is determined and the hormones which cause breasts to grow and have milk glands are formed. Men do not develop, but the nipple area remains.

Women start similarly with a small protrusion inside the vagina that would have developed into a penis had the sex been male.

Answer 3

To produce milk, same as women. It just doesn't come into use quite as often.

There are basically three periods in life during which sexual differences occur. One is in the womb, one shortly after birth, and one in the teens. The differentiation between male and female nipples occurs largely in that last phase. Newborn babies - even male ones - sometimes secrete milk as they are awash with the hormones of being born (it's colloquially called "witches' milk").

And, of course, with the right hormone therapy, men can secrete milk even later.

Answer 4

Fetuses are initially the same. They are all equally equipped.
Later they develop sexual differences because of hormones.
If observing both sexual organ kits (forgiveme for the lack of better words), male and female, both show equivalent parts, though developed otherwise.
See this :
labia=scrotum
ovaries=testicles
clitoris=penis
vagina=sperm canal
Fetus is initially female, but the presence of male hormones, testosterone, provides for the necessary conformation changes.