I was surprised to see how many states had affirmative bans.

That's for good reason - apparently there's been a coordinated push and many of these states have passed these this year. It's being done on the flimsiest of reasons, quietly, in states where the GOP majority legislatures are actively rewriting the rules of elections to favor them.

https://www.npr.org/2024/06/05/nx-s1-4969563/ranked-choice-voting-bans

Brown and other critics of ranked choice voting contend the system is confusing, and he said there are numerous instances in which voters didn’t end up ranking their choices.

“Proponents of rank choice voting claim for it to be a modern solution to electoral dilemmas or lack of confidence in our system of elections,” Brown said. “But the more I looked into it, the more I realized that the evidence and experience had illuminated a starkly different reality.”

Many conservative lawmakers have pushed back against the voting method — and other experts have also warned about “treating it as a one-size-fits all solution.”

If Missourians approve the ranked choice voting ban, the state will join Louisiana, Alabama, Mississippi, Oklahoma and Kentucky in barring the voting system this year. Alaska, where voters approved ranked choice voting in 2020, could see the practice repealed.

Meanwhile in other states, including Nevada and Oregon, voters will decide whether to adopt ranked choice voting later this year.