Wonders of the World is a bit like 2019’s Mystery at the Museum - which I also completed by accident
It’s made easy as every single cache has at least one wonder inside it. It would be more of a challenge if a select few did - so that, if you wanted to earn the souvenirs, you’d make the effort to travel to find the caches ‘containing’ the wonder(s) you’re after. Fewer people would manage it, so it’d be more of an achievement...you would feel proud to have that souvenir on your profile.
I mentioned this in the recent Memory Lane survey, and maybe others did too, so let’s see what happens next year