To the best of my knowledge, party registration in closed primary states is just an additional question on the voter registration form. It's not exactly an oner

To the best of my knowledge, party registration in closed primary states is just an additional question on the voter registration form. It's not exactly an onerous cost unless you're someone who regularly switches which party's primary you want to vote in. That said, even in open primary states, primary election participation is low outside of presidential contests. I served as a poll worker once for a US House/Senate primary, and my precinct got about 7% turnout, and I'm in an open-primary same-day-registration state.