How we've ended up regulating medicine to the nth degree, but when it's teeth we're like "oh well, lol", continues to mystify me.
I'm always baffled by all the discussions about flossing, as it's something that can be very easily verified empirically: one can just floss for a month, then stop doing it for another month, then resume and get a feeling for how the gums react. If they bleed or burn (lightly), then the efficacy is evident; if not... lucky person! No need for research either way.
In my case, I don't need to floss daily, but I still need to do it regularly. Two weeks without flossing, and I'll definitely feel the burn once I resume flossing.
The tobacco industry was a contributing factor but common sense and independent thought was already gone or it wouldn’t have worked for as long as it did.
It's the same phenomenon as something like the calluses guitar players get. If they take a few weeks off, it'll hurt a bit when they play. That doesn't mean the activity improves their health. It means if you poke a part of the body enough it handles being poked better.
One notable effect when regular flossing is sustained is that your whole mouth just feels generally less sensitive and healthy. Less pain when you chew, your breath feels fresher for longer. The reverse can also be noticed when you stop flossing.
As I said, this is not universal since not everyone has the same teeth arrangement. Which is one more argument in favor of not waiting for evidence. It's considerably cheaper to just get some 3$ dental floss, try it for a month, and see for yourself.