That's just it. In Finland sauna is something that is an expected utility in a house like a bedroom or toilet. So while there is research in how sleep or toilet

That's just it. In Finland sauna is something that is an expected utility in a house like a bedroom or toilet. So while there is research in how sleep or toilet behaviour affects health, there is no "bedroom" industry trying to upsell the benefit of having a distinct room for your bed, or a toilet industry convincing you it's a good idea to use the loo.