why do guys have nipples?

Answer 1

It has to do with embryonic development. The early embryo does not have specific male or female features and starts with a basic template that apparently includes nipples. If males are exposed to the appropriate hormones, they develop real breast tissue just like women do.

Other possible reasons are a) God's practical joke on us, or, more likely, b) they are there for guys who like to put piercings through them (had a guy today who had his girlfriend remove one tongue piercing and two nipple piercings before he went to the operating room. He cried like a little girl.)

Answer 2

Starting at conception and lasting until about 14 weeks, all human fetuses look the same, regardless of gender. After 14 weeks, genetically-male fetuses begin producing male hormones such as testosterone. As "female" is the "developmental default" for mammals, by 14 weeks, the nipples have already formed.

Most of the time, males' nipples don't change much past this point. However, some males develop a condition known as Gynecomastia, in which the fatty tissue around the nipple develops into something similar to a female breast. This may happen whenever the testosterone level drops because of medications (like those that treat prostate cancer) and by natural hormonal changes associated with aging, obesity, or puberty.
In the male, nipples are often not considered functional with regard to breastfeeding, although male lactation is possible.

Answer 3

Why do people ask this question without checking to see the previous answers posted the last several hundred times it was asked?