Electronic voting is strictly more expensive than paper voting. All those machines are expensive and you still need the voting places and staff.

If you're willing to do away with the requirement that you can't prove to someone else who you voted for then you can implement mail-in voting. Still paper and you can have an election every day if you want. Some US states use that. Once you go that route a simple HTTPS website run by the government that you authenticate to is all you need for electronic voting with the same guarantees.