Some people perceive it as gross because it's a very intimate bodily fluid and rubbing it on someone else's face (besides maybe your baby's if it has, say, a rash) is usually not too welcome.
Some guys actually are into breast milk, but that is a WHOLE other story (LOL).
Anyway, if you all want to hear some extreme Delta breast milk stories, I have known some women to make BUTTER with the extra breastmilk and then GET THIS: they serve it to their families.