Turns out that very sexy, very boob-y armor you see at ren faires worldwide is impractical at best, and dangerous at worst. Like, if you were gonna do battle over the last deep-fried turkey leg at the faire, your curvy breastplate would protect you about as well as a lacy corset.
You see, to effectively protect your boobs (and the less important parts of your body like the heart and lungs), armor needs to flatten you out. It's true that female armor often needs a different shoulder-to-waist ratio than male armor, but pretty much everything else can — and should — be basically the same.
First, the padding worn under armor — the stuff that makes it slightly less unbearable to don heavy, claustrophobic steel chain mail— practically neutralizes the body shape and makes everyone flat as a slice of peasant bread, according to Tor.
Additionally, breast-shaped armor increases the likelihood that a blade won't deflect — as it would off of relatively smooth chest armor — but instead, it could slide inward and, you know, kill you.
But that’s not all! Let’s say you even fall onto your boob-conscious armor. The divet separating each breast will dig into your chest, doing you injury. It might even break your breastbone. With a strong enough blow to the chest, it could fracture your sternum entirely, destroying your heart and lungs, instantly killing you. It is literally a death trap—you are wearing armor that acts as a perpetual spear directed at some of your most vulnerable body parts. It’s just not smart.
There you have it — if you want a whimsical look that showcases ye olde tits, go for the curvy plates — but if you're looking for armor that actually protects you, make like Brienne of Tarth and get your flat-chested protective/ass-kicking armor on.