But your comparison is inexact, because smoking is medically a bad thing to do, and something that most people would be better off not doing, while sex is something that we expect most people WILL do at some point, and which is a natural activity which is not something doctors would generally tell you to avoid.
I don’t think my doctor has ever given me a medical opinion about guns in my house though :-)
I also mentioned eating. Is not eating necessary? Is it not a natural activity? In fact it is more essential than sex. Yet doctors tell people to eat less all the time.