For the same reason loosening/liberalizing laws of any sort is met with fear and resistance even from the people who should "get it." When something's been "this way" for more than a generation or so the people who live under those constraints tend to become pretty comfortable with the status quo. It goes from "this sucks," to "this is how it is," to "this is how it SHOULD BE! It's OUR WAY and don't go telling us we should change!!!" Folks start to see the laws their forebears voted into being as generally good, right, and proper, even when everyone else sees them as absurd, pointless, insulting, and tyrannical. It isn't just open carry, either. We've seen members argue against "constitutional carry," argue FOR universal background checks, argue that there SHOULD BE prohibitions on carry in banks, churches, schools, bars, sporting events, etc. The fact that there are impeccable examples of states without said restrictions and infringements seeing nothing but positive results doesn't seem to impress many people. It's not "our" way. That's not how "we've always done it." That takes time to break down, if you can even manage to convince enough brave folks to support removing the stumbling blocks from their own path.