Usually it is in response to people who have oddly specific criticisms of a woman, such as thighs being too wide, or shoulders too wide or any of that stuff, who need a reminder that they're not Brad Pitt.
Some Dude 2:Ew, her thighs are like, way too wide. She's kind of ugly.
Some Dude: Yeah, I see what you mean, bro. Elbows too pointy as well. 1/10, would not bone.
Adam: Man, have you seen her elbows? Would not hit it!
John: Damn you're right brah, elbows too pointy.