first 
how do you establish identity? one verified voter identity oer private key, right?

and even if you can, people cant even be trusted to control their private keys when its their families wealth.
with the apathy around voting whats to prevent "custodial voting solutions" from evolving?
not to mention just the realistic possibility of large scale basic private key security.

considering the logistical and educational hurdles
we're still better off with paper ballots