It’s also bugs that we can see. Nowadays people use lightboxes, have electric lighting in their homes, typically wear eye-correction lenses if they need it, access to resources on what’s infested and etc, and there is more awareness. Plus there are more alternatives to choose from if something is forbidden.
Generally I think the average person today is better able to spot insects, and thus see what’s infested and cannot be eaten. Plus one isn’t desperate.
Also… Maybe back in the day rabbis were stringent about checking, but now they decided it’s not even worth it because people can just eat something else.