My question is about Hijab. I understand that due to the difference in the biology of male and female, we have different needs. However the thing that i do not understand is why women have to cover the hair and neck, while men do not; of course, i understand men have awrah and hijab obligation too, but why do they not have to cover their hair?

Your answer is in ur question, they are created different biologically and they have different feelings, different needs etc

Hijaab of women save her dignity plus family relationship plus society needs.

Man is hard, decision maker, have mange family etc so he have to live different way in society

In short all is about obedience