I think the simpler answer is, you are so right, it barely has to be valorized. It sells itself.
I think the long answer is that porn addiction is a real thing that can affect people. Also lots of people in charge of things like sex education have historically been prudes who see masturbation as some sort of gateway to promiscuity.
While orgasms are normal and can potentially have some physical and mental benefits, there is no physical or mental necessity to have them (plenty of asexual and otherwise celibate people of all different kinds out there to prove it).
the "mental harm" is having to walk around horny all the time, constantly thinking of sex, and affecting your interactions
this is not a problem which normal people face. if you are constantly thinking about sex, you may have an addiction or an otherwise unhealthy relationship with sex
I mean addiction colloquially. The existence and over use of porn does cause some people and their relationship some level of affects. I don't think we can just hand wave it all away.
You are preaching to the choir here. Yes I can believe porn addiction only exists in the kinds of the those in the religious community. I'm still trying to provide a larger picture to answer the question of why the government doesn't tell you to masturbate every day.
Porn, for some people in contexts, has had drawbacks. Those people, in some contexts, have curtailed the valorization of porn writ large. Maybe this campaign has biased me to a degree as well.
I have never been to a Sex Addicts Anonymous meeting but I'm not about to write the whole idea off entirely.