Its simple as this because it was Guru Gobind Singh Sahib jis hukam for Sikhs to keep their hair. For a Sikh there should be no other Skeptic thoughts after this. But we are Skeptic people and we want to know even more and more. In other words we want to know everything in this world and the universe, but even knowing everthing in this world is useless if you dont accept Guru ji.