Why do we use the really awkward, blackbox and sometimes networked machines that we do, manufactured by weird companies rather than whoever makes scantron machines or whatever?
Because they’re cheap, states have to fund their own elections, and no governor will ever fund an election over schools or infrastructure.
The real question is why elections are not federally funded. The answer is that states are afraid election funds will be withheld over speciously related issues, just as highway funds are withheld over drinking ages. IMHO the correct change is a constitutional amendment guaranteeing federal funding for all state elections that can’t be withheld for any reason.