This is no way to live for a young guy...
As men its in our genes to impregnate as many women as possible to ensure our survival of our species. Man was/ is not "hardwired" to settle down with one girl for 10 years and be loyal to her. Women are however, design this way. They are hardwired to pick up on men with masculine facial characteristics (strong jawline, thick eyebrows, large noses, prominent cheekbones) as it signals high natural test levels. Yes they find men with these characteristics sexy as they are indicators of good genes, but its a catch 22 as men with these characteristics will have higher sex drives thus be a potential risk to the survival of her future offspring. It is her job to get to know this sexy man and reel/sucker him in before she gives him access to her egg. This is the reason I have no respect for a woman who gives it up on the first date ...... She's not even a woman to me...shes a shitty future mother in the making, a biological failure.
I agree with some of your points, and disagree with others. Since I feel like typing today, let's launch into it.
I believe it can be a way for a young guy to live. Certainly not most of them, though. So maybe you were generalizing. But some young guys do like stability, and young in age doesn't necessarily mean young in terms of maturity, or life experiences, or what have-you. One of my good friends married at 21 and is very happy. He spent his youth in and out of foster homes, in reckless relationships, etc...he married when he found a great woman and he was ready for stability...not instability. So it's not a "young" in age thing, I counter, but an "experience" thing. And there are of course men out there who are very experienced in a number of relationships who have no desire to commit to one woman. That's fine too. My point here, would be that we can't generalize. To each his own. For some young, and old men, stability is more important that multiple partners. For other, the inverse is equally true. I would submit that there are more men seeking stability than instability; if I were wrong, marriage would have never taken hold worldwide. Clearly, committed relationships provide an advantage for passing along one's genetic fitness. Let's explore why, perhaps...
Secondly, though I appreciate the comments on "nature", one must also accept that man is just as much "nurture" as he is "nature". The very fabric of a functioning society (which we are all part of) depends almost wholly on man being able to use nurture to bend his nature to what is best for the whole, and not just himself. The creature that is man is far more genetically successful when banded together, than when standing apart...a well-held tenet in the ever expanding theory of evolution. An intuitive understanding of this has led men to create society, and societal norms and mores that govern how we behave. Part of those norms involves that once a man and woman commit, that no one should come between them. And secondly, that man and woman should commit to each other if the purpose to have children (as stable homes make for stable children, who make for stable adults). And the ultimate purpose of sex is to create children (you are genetically hardwired this way, and it's hard to repress these feelings...men and women feel them both, in different ways). Therefore, engaging in casual relationships for sex and not children goes against genetic predispositions, and also goes against societal norms; it is an unconventional way to approach life, and in general, unconventionality is ostracized and marginalized, which is no surprise (monster rhymes).
Whether you believe this theory to be true or not is up to you, but rest assured, the man who carouses and wenches in any society is quickly ostracized. I'm sure he may pass along his genes to women who enjoy his company (being unfaithful is nothing new to humans), but he will not tend to succeed in society, in general (there are always exceptions). That's why most men, though their nature compels them to become a modern-day Johnny Appleseed, become committed (or at least mostly faithful) spouses. Society is generally more tolerant and accepting of this behavior, allowing the man to build his wealth and status, and create a more stable environment in which to raise his progeny to ensure their success as they mature (you can't argue that the man who sires multiple children out of wedlock is doing the right thing by his children).
You raised the "gene" thing, so I thought I'd respond in kind.