Banks, hospitals, airlines, rail systems, and automakers are all on the hook - if their system does the wrong thing, someone will notice the unbalanced books, bodies, or wreckage (other banks, Treasury, NTSB, NHTSA), and the institution will suffer serious harm.

How will you know if an electronic voting system produces a wrong result, except by running a paper voting system in parallel?

Do municipalities choosing voting machine contractors have incentives aligned to promote election integrity? Can they critically evaluate security properties of what they're being sold?

I don't think so.