The short answer, men ARE part women, XX and XY chromosomes and all... there is a more complicated answer, but that escapes my mind as of now.
Men don't "have to," but it is weird if he does not because EVERYONE, men & women, have nipples.
No, you must not forget that only Hawaiian men with out penises can have have large breast but no nipples
Your nipples are probably not "sucked in", but simply inverted. Some people's nipples are just naturally this way, and is not harmful or bad in any way. Everyone's breasts and nipples vary wildly, despite what you see in the media. Inverted nipples are not normally an issue for breastfeeding or anything else. Surgery is possible to change the shape and protrusion.
Shaved obvs, hairy nipples look like spiders like bevans
Nipples come in all sizes; men's nipples also can range from very small to very large.
We don't. They get hard when it's cold or some women get hard nipples when they are aroused. Same reasons some men have it actually.
Penis (in men) Clitoris, nipples (in women)
Yes, there are different types of nipples in men, just like there are in women. Some men may have protruding nipples while others may have inverted nipples. Nipple size, shape, and color can also vary among individuals.
That women can do as much as men when you set your mind and heart to it
Yes, I think many men do. First many men like women with curves. I do and I love large busty women and I do not mind a belly either.
no, if u r cold your nipples tend to get hard. Women will most always get hard nipples when aroused and most men wont, but some do. if u r Mae and get hard nipples when aroused it doesnt mean theres anything wrong it just happens.