Formerly research fellow @ Open Phil, now freelance. Mostly on Twitter.
More the latter - I think it's hard to influence the UN, especially if you need security council sign off. Really, you have to influence every country on the security council to agree to more peacekeeping, and also come up with more funding somewhere, and UN bureaucracy is famously difficult and impenetrable.
Would I love to redesign UN peacekeeping to focus more on rule of law and less on soldiers? Absolutely. Do I think there's much possibility to do that? Not really no.
I should note - I don't think peacekeeping is anywhere near as cost-effective as GiveWell's top interventions!
My (very quick, rough) BOTEC on peacekeeping in 2022 had it about half as good as GiveDirectly (see the civil conflict shallow and associated BOTEC). Peacekeeping should not be an EA cause area. Getting the UN to focus more on peacekeeping and less on other functions? That might pencil, since it's leveraged (though I am very uncertain on that).
Also a longer response: I do think the lack of demand is worrying and could be suggestive that these studies are not showing real world effects. I haven't spent enough time in rural Kenya to know how hard it is to get glasses, but I am updating based on what you say!
I do think it is easy to underestimate how bad your vision has gotten and not use glasses you need. Personally, I have failed to notice that my prescription has gotten out of date and continued to use old glasses, and then finally get around to getting new ones and I do notice a productivity improvement. Since your brain can somewhat compensate, I think it's easy to underestimate the returns to a correct Rx.
I am very excited to see your longer comment when it's done - make sure to sent it to both OP and Erin Crossett at GiveWell as well; it sounds like we will all benefit from it!
I haven't seen a lot of evidence on other kinds of peacekeepers, so I don't know that I can say with confidence how effective they are! I would guess it depends on how much they are seen as a neutral third party.