If you called the hijab "a simple headscarf" in front of the liberal Muslim women I work or I'm friend with (all from Tunisia except one from Lebanon), you'd wish you hadn't. Seriously, speaking of the hijab as something we shouldn't really notice anymore is something that makes many liberal Muslims I know really annoyed (or very discouraged).

I can't speak for Europe, but here the estimates are that about 15-20% of Muslim women here wear the hijab (cases of burka, niqab, tchadors exist, but they're much rarer).