They don't all have it but it seems to be less common, at least in this country. Its a misconception (by black ppl included) that all black ppl have curly hair. I thought that too before I joined NC.
I think one difference is that white ppl are less likely to come right out and say it. Whereas black ppl are more likely to be like "you need to do something to that hair!"
I think black ppl care more b/c of our own self hate about "afro textured hair."
As far as dates/interviews go, I think its pretty widespread...no matter your culture/color, you get social pressure to straighten your hair for these types of events. I've heard this from friends with wavy-kinky hair. I think that's something we're socialized to believe. Its the whole idea that any kind of curly hair is somewhat unkempt.