How come Muslim women don't put a hijab?

i thought being a hijabi was a personal choice? why do muslim women and men criticize each other so much? pakistani women don't cover and from their own mouths i've been told that there is no reason to in pakistan because everyone is muslim so you don't have to. although in the Qur'an muslimahs are told to cover. i've seen many protest signs and profiles insisting that covering is a personal choice, but from the outside looking in, it seems that if you don't, you are heavily pressured or looked down upon by your sisters and brothers.