This just keeps bothering me, /e/. It's in every pixiv picture, every hentai anime, every eroge, and almost every fanservice anime. Look at this girl's nipples. What the heck are those dents/holes?

I know that some girls in real life have those, but it's very rare! Search for real nipples in google, and you will see that most don't have these dents.

http://bluf93.deviantart.com/art/nipple-198973117
http://fergiefoto.deviantart.com/art/Nipple-squeeze-101203721
http://pssst-you.deviantart.com/art/nipple-133530259

So why do artists keep drawing dents on EVERY character? Why can't they just occasionally draw characters with normal nipples?