---- Guru Nanak Dev Ji, as far as I know, never asked his followers to keep hair. ---

Veer Jodhbir, We dont know what Guru Nanak did, said. We just guess from the history. So I am not sure, to what authority You or I can say something like this.
u r right, when u say that wearing 5Ks doesnt make a person noble. In other words, a person without these could be far better in deeds compared to the latter.

By saying all this, we are going as per outer appearance, the superficial one only. Lets get one step further. 5Ks is the baana, which is a part of others i.e. Baani, Baana, Simran and Seva. A person with Baana only cant be assumed to be having other 3 also, right? But he/she is supposed to have those four. The one who has is the Sikh.