> What's the benefit? What do we gain?

Probably more flexible voting systems would be possible. In various countries a) there's a trend to ask voters directly about secondary topics and b) there are reports how voting organizationally is often a mess preventing people to vote within the available time window. e-Voting would enable counting votes quickly and do fraud detection in a more relaxed time window.

So yes, there's a case for being able to more flexibly cast a vote. While more direct democracy isn't there yet for other reasons as well, paper is a technical reason.