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human
[Wonder Woman] Why doesn't Wonder Woman wear protective body armour more often?

It is known that Diana actually does wear some kind of Amazonian heavy armor on some occasions, but only during special emergencies it seems. In her regular superhero duties she dresses normally in her regular uniform, but this lighter attire makes her vulnerable, does it not? I mean, just how protective is Wonder Woman's regular costume anyway? 

If she is vulnerable to conventional bullets, then why doesn't she just wear either some modern ballistic body armor or her own people's magical body armor, at all times? Aren't blades and sharp projectiles her only major weaknesses? So if body armor can counter these...

It is true that she has her unbreakable Bracers and super speed and reflexes to avoid incoming threats, but despite these boons she has been notably successfully shot and/or stabbed by her adversaries repeatedly throughout her history, and has suffered terrible wounds each time. Each time this has happended she wasn't wearing her heavy armor, so it is suprising that she hasn't adapted to this yet.
gpt
Broadly speaking, heavy armor versus light armor is all about tradeoffs. Assuming they are made from similar resources (i.e. similar levels of magic, technology, etc.), a more protecting suit of armor is going to limit endurance compared to light armor. This is due to the increased weight, but also in how it traps body heat and intereferes with the natural cooling mechanisms: even if you are more than physically strong enough to bear the weight, you're still in danger of overheating. Overheating in heavy armor was a very real hazard to armored knights for instance, and in some cases is believed to be directly responsible for fatalities; for instance, some of the French losses at Agincourt were due to knights having to slog through muddy fields, wearing themselves out from heat and exertion, collapsing or being trampled, and drowning in a few inches of water. 

For a more modern comparison, consider the average patrol officer (who wears at most a ballistic or anti-stab vest) versus an armed response/SWAT officer (who shows up in at least a DOJ Class IV vest and combat helmet, likely more). The latter is more heavily protected, but the former has fewer handicaps on their endurance and mobility. For a patrol officer, the trade off isn't worth it, since most of their days are going to be spent patrolling, investigating, or otherwise doing things where fatigue is an issue. SWAT, meanwhile, specifically kits up that way because they are planning for a potential fight, with a fixed duration, a controlled perimeter, and other proper planning; if someone bolts on them, they don't need to run them down, that's what the security cordon is for.

It'll vary from Wonder Woman to Wonder Woman, but for the most part the lightweight armor is considered enough for "day to day" use. When Diana is going around, being the Ambassador to Man's World, hanging out with the Justice League, she considers the one piece and the bracelets enough. When things start getting real (and she has the time to do so), the heavier armor can be hauled out.