@Atlas47
Well there are some logical reasons for the "bikini armor" in fantasy settings, though defensively there's no excuse.
Even chain mail is quite heavy, on someone who's not muscular (like a mage), armor is just not viable, however in the case of bikini armor, it's use would be based on things like magical enchantments (if one put a permanent barrier around your revealed areas especially, then the argument makes sense), i can't remember the manga's name (it was a level 99 cook manga), but one of the characters in it wore bikini armor and was asked about it, it had several enchantments on it such as a speed and evasion boost, but it also had the added benefit of "distracting" enemies, and outside of dungeons she usually wore a cloak, while we today might not be effected as much by such, remember that in the past, women rarely wore anything that showed any skin outside of hands and face, for religious and in some cases, obvious reasons.