Korean Attitudes : Embarassing to speak english in public?

I noticed this with some of my Korean-friends, attitudes suddenly changed and phone call wasn't as fun and free as usual hehe.. when i asked why, they admit that they felt so embarassing to speak english in public.. once i called my friend when she was in a public space so she couldn't say anything. She said It would be fine if she could just speak Korean to me, but oh well... I won't understand that ^^; So for her, she just didn't want people to look at her coz that's kind of embarrassing.

And my friend said almost same thing :

well, when we were talking, there are lots of people around me looking at me like "wow, look at him. he's talking in english on the phone." so realized that strange atmosphere, i couldn't concentrate on what your saying. shooot. it was really really bothering me. they didn't even know me. but they were starring at me and got me shy. ^^;

Anyway...I do have some other Korean friends who won't feel shy to speak english in public but.. i think in general, for Korean people, in a public space it's really unusual to hear english speaking Korean unless you are so confident with your english, if your english is real good as much as people would envy you, then you can speak it loud ^^ so nowadays when i call my friend but she is in some places where speaking english is kind of embarrassing, then she will just give me a sign by saying "unnie~ mi an"

So complicated -_-;;;