The real reason is people who decide on this are 60+ years old and full of prejudice and fear of new.
They can state the problems of the new but the do not see the problems of the old.
Attack surfaces you say ... manipulating the elections is easy not matter what... comparing manipulation of paper ballots with mouse clicks is false dilemma.
We have no big problems using electronic money.
Q.E.D.
Pretty condescending view of people who want to use new technology when it improves their lives in some way, but don't prioritize making every aspect of their lives revolve around them.
What you overlook is the huge importance of the 150 million people who voted being able to interact with civic minded volunteers at polling places and being able to see video of the the state by state counting process. Including observers from both parties.
That is a key reality check feature in this election when a large portion of the Red voters are willing to believe fraud and conspiracy claims.
A significant portion of those voters, having witnessed the process with their own eyes, will reluctantly accept the election result and not join the nut cases in civil disturbances and attacks on the state electoral systems.