The key is to find the hole on every single flat, and know the tube orientation and tire orientation to identify the exact spot. Every. Single. Time.
As said above, tiny sharp things can get embedded in the rubber and only show themselves when the tire is being flexed by rolling. Finding the location will point to where the problem lies.
In 50+ years of cycling, I've thrown away exactly one "cursed" tire where I could not find the culprit after multiple flats. Something was there, but it defied being found.