Kareena, This is the problem. Majority of people doing something can not be considered as right. In islam Hijab is a must. There will be more people to support you when you go against the teaching of your religion. Those non believers are happy when you join with them and accuse your religion. You can wear whatever you like then don't call yourself as muslim. To be a muslim you have to follow the teaching of Islam. You have to perform obligatory prayers. You should be aware about the AWRAH. That is why Islam teaches you what and how to wear.
Lusitano, Islam doesn't look on the quantity but quality. No one worried to have more followers of islam if it is not in a complete way. If you do something, it should be done sincerely.