It might be common sense if you work with statistics, but most people don’t, and the only way they would know these things is if someone says them.

Regardless, it was the top comment so people clearly think it was valuable enough to vote for.

Nature isn't an arbiter of truth, it's a publisher of papers. It's also meant to be read critically by people who see a paper like this and and think "interesting, but this is just an observational study, I'd like to see more research, maybe something with more controls before I believe this".

Say what you want about the "correlation doesn't imply causation", but many people do not understand why that is. As a shorthand for "hey, you don't know the statistics behind this, so don't take the pretty picture at face value", it's pretty good.