The thing is, your grandma can watch a paper process, understand it, and verify that no shenanigans happened during the part that she was watching. But she can't do the same for online voting. She's not going to audit the software used. She's not going to verify network integrity, or authenticate packets.

The manual processes are much better for transparency and verifiability. And we really badly need those qualities right now, when you have to be able to prove to the other side that the vote was legit, and be able to prove that every claim otherwise is false.