@breizh not all people comfortable with armor on their chest tho... and she clearly says that he more comfortable with her current outfit...
and not all 'adventures' need to wear armors, class with agility like shinobi or assassin, that need to move fast and flexible, having chest armor is hindering their movement, there's video on youtube, people try to running with chest armor on them, heavy and hard to run... so yeah, rather than having difficulty to using their agility and die pointless death, they rather have light clothes and using their agility to dodge enemies's attack..
easy example look at Gymnastic outift, it basically just one piece swimsuit, or athlete runner...