Obito's eye was implanted on Kakashi, not the other way around. Kakashi's sharingan was originally Obito's, which is why Obito can see through his eye, which is on Kakashi's socket.
Kakashi is unable to see through Obito's eyes because it is not Kakashi's eye that was implanted on Obito.
Use some logic and you will be able to understand.
I also have a hunch that if Obito and Kakashi goes closer together, then Obito gain the ability to see through Kakashi's eye, which is the reason why Obito only saw through Kakashi when he was drawing near to Kakashi's location.
Or I maybe wrong, and Obito can see through Kakashi at any distance.