The act of sex releases chemicals which are beneficial to the body because we're doing what nature wants us to do -- which is to have sex.
Nature is not a person with a "will" - therefore it cannot "want" - it simply exists.
Which means nature thinks we're making offspring.
Sex is not just for pleasure and to heal the body.
But it is
for it - whether it is
just for it or not is a moot point.
It's to get us to make children.
If it feels good, that's because we're doing what nature wants us to do -- reproduce. At least the body is being tricked into thinking that's what we're doing.
Much like watching an action movie or playing a video game "tricks" the body into thinking it's viewing a gun-fight. Thereby releasing a satisfying adrenaline rush. However the "purpose" of adrenaline - it is to escape an actual flight-or-fight situation. This is just deception of the body
I think nature would probably like it if we reproduced all the time. Or we tried to keep reproducing, at least.
I think if nature had the ability to "like" anything - I think it would like it much better if people with no will or means to support children didn't have them. And I think it'd be more worried about overcrowed orphanages, and starving North Korean children than other people's private sex lives, or an elderly couple having sex (which I assume you're against for the sake of consistancy - since they can't have children, right?)
That's why people will roam around and have sex with different people, even if they shouldn't.
Ah but they should. So long as they use protection( or avoid actual copulation) then they're far more healthy than those who practice sexual repression based on ignorance of the subject matter.
The dangers of smoking or eating nasty fast food are far more dangerous than those of having sex - even if a person was an actual swinger they'd still be putting themselves at far less statistical risk.
People rape due to sexual repression (and a bit of sociopathy doesn't hurt either). Serial killers such as Ed Gein, and serial pedophiles such as those priests in the Catholic abuse scandal for example.
Having a healthy sex life removes any "benefit" from rape; much like being well-fed would've alleviated the Donner Party's desire to cannibalize each other to survive.
The sex instinct -- the drive to reproduce -- is making that happen. It is not just for enjoyment and relaxing. Its primary purpose is to get us to produce children.
In the modern world it's primary purpose in practice, is pleasure, not to have children. The number of times a normal couple has had sex for fun definitely exceeds the number of times they've had sex "planning" to have a child.
As horrible as it is, I think rape is actually a natural instinct, although a very savage natural instinct. My man, Sam Harris, actually agrees with me as I've heard him say this himself.
A female dog goes in heat and a male dog goes and mounts it. A dog will hump your leg. It's the instinct to reproduce. It's what we're designed for. Rape is sex where the woman did not want to be having sex with the man who raped her. It's unwanted, intrusive sex on the person who has the right as a free human being to not be violated. But outside of all of that, it's based on biology and the instinct to reproduce.
And who would a woman want to have sex with less than a sexually-repressed religious indoctrinate who gets squeamish at the sight of a woman's breast (yet at the same time probably tells you he's against homosexuality?
This reaffirms my point that sexual repression causes rape, not a healthy sex life.
If sex boosts testosterone in men, it's because it's a reward for having sex.
Or masturbate. Or foreplay. Etc. "Yawn"
The man has accomplished something he's designed to do.
Your view is based off of religion and has no factual basis to back it up. It's just "begging the question".
I also pointed out your double-standard above with a few analogies - if your outlook was remotely consistent then it would not apply just to "sex" - it would apply to other forms of "pleasure" as well which serve no survival purpose (such as food seasonings, video gaming, movie watching, posting on message boards, etc). The fact that it ignores this consistency shows just a religious fixation on "sex" and nothing more.
Not to mention traditionally men took multiple wives and concubines, and men played little to any role in raising the child (this was a primarily feminine role) - so if you're trying to appeal to tradition, or what men have been "designed" to do - then you open that can of worms as well.