It’s a complete mott and bailey. Obviously 95% of people can avoid back issues by just working out a few times a week. But when you point that out you apparently just happen to be speaking to the one person who has severe scoliosis and it’s implied that that’s who all of the people complaining about bad backs are dealing with.
It’s an identical situation when you talk to people who complain about sleep or diet issues.
I think you’re missing a key point. Archaeology doesn’t look at every single thing from 2,000 years ago. All we have are sparse records of a small fraction of artifacts that happened to be preserved against the odds due to anomalous natural events. Nature could preserve a few long into the future.