Because this all tradition/culture came from the ancestors and there ancestors. It has been followed till now. So the men think women are inferior to them.
This is totally wrong we should treat men and women equally. The people how thinks women are inferior to them should change there mentality and should treat them equally. If one elder person of family starts this then there successor will do the same. The possibility of this is 99%.
Generation by generation  it has being followed.

We follow that what our ancestors follow. We can change this by treating them equally and so our successors will follow.