Well it becomes a issue when the government has to pay out cash, for the consequences of things like drug abuse, divorce etc.
Although this is true to a point, it's very easy to get on a Faustian slippery slope here. To what degree does economic benifit outweigh having an omnipotent government that can tell you what to do behind closed doors ??
Homosexuality has increased medical costs associated with it. Does that mean Gov should outlaw or put a tax on it ?? How would you enforce that ??
What about these winter mountianeers who get stranded and 5 million dollar search and rescue efforts are needed to save them ?? Should we regulate mountian climbing too ??
Liberals complain about gun violence and liberal attorney grops have tried to sue gun makers for damages. At what point to you call an end to this ??
And finally, what about abortion ?? Economists Steven Levitt ans Steven Dubner, along with several leading criminologists, have found that and INCREASE in the number of abortions leads to a DECREASE in crime !! Should we mandate abortions for low income women who have alcohol/drug abuse or crime history ?? The science tells us that this would be a GREAT idea !! (I'd almost agree myself)
You can use economics and pragmatism to rationalize almost any government regulation of our day to day lives.