i think it is a reasonable question and am glad the op asked instead of jumping to her own conclusions as people seem to do on here,
there is a hadith which says something along the lines of : " you may think someone is from the people of paradise, when really they are from the people of fire, and you may think someone is from the people of the fire, when really they are from the people of paradise"
the meaning is clear; you cannot judge from outward appearances, and you do not know what is in anyone elses heart, even if someone seems very pious, fasting praying, always in the mosque, they may be doing unseen sins, such as backbiting, interest, or oppression, or may hold unclean thoughts etc
As a muslim i know i wasnt born wearing hijab, and none of the muslims i know were either, so we all had to come to our own conscious choice, at the time we had our own personal realisation and understanding to wear or refrain from wearing hijab/abayah/niqaab many people i know have been through multiple phases and combinations, before finding whats comfortable for them, and fits in with their own personal beliefs and interpretation of the deen.
knowing that, it would be very hypocritical of me to judge others who didnt wear hijab/abaya/niqaab as i didnt do it straight away myself.
I would however add that i would judge those who claim to be muslim but deny the clear laws of Allah.
I know i am not perfect and i sin, to sin is to be weak and human,it is our nature, but i wouldnt try and justify my sins according to my own desires.
by this i mean those muslim women and men who look down upon those who wear hijab as backwards etc