One person willing to go to jail for being caught double voting or voting illegally can change the total vote count by a single vote. There is no evidence that enough people are ever willing to take that chance to swing any election. One person willing to risk being caught hacking a single voting machine can affect hundreds or thousands of votes. (But think about computer viruses, they rarely affect just one computer).
Go after a state with many electors and a hacker can change the outcome of elections up and down ballot and thus the future of a municipality, a state, or the whole county.
The stronger the penalties on hacking that affects our very government, the better.