this is a characterictic common in some Japanese girls. Mostly who have this chacteristic act strange. they are careless and make many mistakes. they are easy going so they don't care their mistakes and no one can blame that ,because she didn't do it on purpose. some japanese boy think that cute.
Actually, if you're talking about FRIENDS and 天然ボケ, then Phoebe is
DEFINITELY the 天然ボケ champion. Haha.
But I think that for Japanese girls, 天然ボケ has a social purpose just like
what you explained, Yuri. It's becaause Japanese society (in particular,
Japanese men) think it's cute.
Quite coincidentally, in my Canadian studies class, I have a very good looking,
kind of ちゃらちゃら 金髪girl who always talks in a ギャル系 kind of way.
She almost tries to show that she's not intelligent. But every class of mine
she takes, she is ALWAYS at the top of the class. She's VERY intelligent. So
why does she always do the 天然ボケ thing? I guess it's because it's considered
cute.
But I think deep down she knows that she's smart. At least I hope so!