Voting is a really hard problem: beyond the massive and likely intractable security problems[1] you start getting into problems with knowledge. Say you push out a vote on a big trade deal or a proposed change to the healthcare system – what percentage of voters have the time and knowledge to even evaluate the options? What percentage of them have time to do so before the deadline?

1. Consider how you'd handle an employer coercing their employees to vote in a particular way. Absentee ballots are already a problem here but they're not used frequently enough to be decisive in most elections.