In Japan, it's extremely rude to say 'thank you' to compliments given to you. You're supposed to say "oh no, I'm not <whatever the hell you complimented them on>" or "No no I have a long way to go."
Maybe it's because they're full of self loathing (like me) and find it difficult to understand why people would pay them a complement because they believe themselves undeserving
People are insecure, not to mention how it's pretty much considered a virtue (especially for women) to be self-deprecating. When someone says "You look good in that dress." Most are raised to answer along the lines of "Oh no, this old thing is just what I had in the closet." no matter the frantic shopping and grooming that led up to it.
We're not supposed to agree that we look good. That would make us shallow and up ourselves.
"You look good today."
"Oh no, when I left the house I looked like shit, you're just saying that to be nice; Don't pity me, asshole!"
:l