Yeah um this trend is over here in the US as well. Get with the times buddy.
I think Polish women are tired of being Polish. So they dyed their hair black.
Actually, there's been a study done on hair color in Poland and it's pretty even with about half of Poles falling under blond/dark blond/light brown and the other half falling under medium brown/dark brown/black.
One thing I find weird about this site is that some people on here try to make it seem like Poles have a monolithic look which is far from the truth. The Polish population consists of many different looks. Get over it.