Answer: because he didnt awaken it naturally on his own, it was given to him by Hagoromo gave half of his chakra to Sasuke, which led to his left Sharingan turning into a Rinnegan. therefore he cant deactivate his rinnegan. You can only deactivate it if you have acquired it yourself. If it’s deactivated there will be no tomoe in it. When activated there will be tomoe
Step-by-step explanation: