Why do Sikhs not accept any other Human Gurus despite having had 10 Human Gurus in their history?

In reply to your question, the undersigned wants to say that the First Guru Person, Guru Nanak Sahib, in his discussion with Yogis, had made it clear that his Guru was Shabad, when he said (ਸਬਦੁ ਗੁਰੂ ਸੁਰਤਿ ਧੁਨਿ ਚੇਲਾ). Nine Guru Persons, who came after him, came with a mission from Akalpurakh and when the mission was complete, the Tenth Guru Person, Guru Gobind Singh ordained Guru Granth Sahib (Shabad Guru), as ever living Guru of Sikhs. Therefore, Sikhs don’t accept any other Human Gurus.