Bikini Armor’s equivalence is Chip-and-Dale Chippendales armor. (EDIT: Oh snap, I confused the Disney cartoon with the strippers, lulz)

Boob Armor, IMO, is equivalent to Codpieces. People sexualizing armor, because sex is that much more awesome when its made into metal.

Like, look at this Greek Armor.

Its obviously there to demonstrate masculinity and look sexy on the battlefield (or play-battlefield / parades / ceremonies).