not just 10 gurus!
guru granth sahib contains baani of 52 saints all together from every available religion at that time. it doesn't contain bani of guru gobind singh as he was the last guru and a guru never declare himself as a Guru to anyone except his followers(who have his grace) in his time. after him there was no successor for the gurgadhdhi. so no-one dared to make changes in SGGS. hence, they made Dasm granth which is bigger than SGGS itself and contains baani from Guru gobind singh. due to lack of devotion and guidance, there is no proper translation to it too.
it is crystal clear if you understand or study SGGS, sikhism was not a religion. it was a new path and new way to god for humanity. but us, the so called successors of our Gurus made it a religion. there is a great difference between an army and citizens of a country or a khalsa panth and sikh community respectively.