Since you asked; My first (understandable) answer to it will be “Because I don’t lend you my eyes and because you don’t know how to be Me.” Interestingly there is no end to this idiocy of asking Why’s after Why’s yet most of the intellectuals among us continue to suffer the limitations of their individual intelligence.
As per Tantric view the first feeling (of seeing from my own eyes and not anyone else’s) is caused due to Niyati, the limitation of space. You, by strong association become fixated to your own body. And What you asked as second part of question happens because there is this (though false) individuality operating at two levels i.e. Ahamkara (objective ego) and Purusha (Subjective ego).
However Masters tell us that, breaking through or transcending through these limiting experiences is very much possible and you can then in real sense shall be able to see from “My eyes and not Yours” and also having experientially tasted different bands of subjective-objective consciousness such as ‘Aham-Idam’, ‘Idam-Aham’ through spiritual practices of Tantra this boundary between I and You starts melting down.
For the fact, you should know that when all these limitations fall apart first time we experience that it is I who is operating through every single speck in the universe. I am The source.. I am the world.. I am you.. I am everything.
– Acharya Agyaatadarshan Anand Nath