Sorry but when did I talk about non-hijabi women? Of course I've met many non hijabi women who are very modest and do value themselves. I do think you can still be modest without wearing hijab.
However, my point is directed at the purpose of hijab. A hijabi woman may use hijab as a way/tool of objecting the whole concept of objectification of women.
Women who dress more modestly - physically take a stronger stand to object this whole idea. (Although both can feel as passionate internally).
For example, a woman dressed provocatively can equally feel very strong about the fact that all women should be judged based on their personality and not their bodies. Well, it is kind of contradictory because they dress provocatively but at the same time they feel passionate about objecting this whole idea.
There are two types of modesty, internal and external. Women who wear niqab should be given the credit of being more modest externally, although It is not compulsory at all. I don't see what your point is here.