Theoretically it could also reflect the society. If 80% of people aren’t religious at all, then at most 20% are more religious than average.
So while you could imagine a society where 80% of people believe they aren't religious at all, the United States at least does not appear anywhere near that number.
https://www.pewforum.org/religious-landscape-study/importanc...
(You’re probably right anyways - there’s a reason I put ‘theoretically’ at the beginning of my first post)