A mere five years ago I would’ve agreed, but now I actually take issue with the whole “It’s fine as long as it doesn’t hurt anyone” stance, given how completely irresponsible some grown adults are.
Society isn’t a random assortment/collection of enlightened individuals; we’re social animals who learn behaviors from one another. When someone starts to act in ways that are self-destructive and we permit it because “it’s their life,” there will be others who will look to emulate that and think it’s fine because it was permitted in the first place. Then there will be others who will copy them – It’s a domino effect. Before long you get an increasing number of deviants who will try to reshape society for their benefit, and don’t afford you the same kind of permissiveness you gave them: Which is exactly what we’re going through now.
It is about society’s physical, mental and emotional health, and preventing foolish people from making decisions that they would likely regret later in life. A nation and its people are like a household and the family that resides within it it – You look after it because it does affect you and those you care about, even if indirectly.