[Actually, one could make the case for it. 50 years ago, it wasn't needed. Now, many men are reluctant to get married 'cause they're getting the milk for free.]
As a single man, I have to admit that I get surprised and learn a lot on FR. For instance, did a lot of older men in American society really marry partly because they would finally be able to get sex? I guess before 1968...that actually was the case. Wow! I think I remember reading about that in a history book somewhere.
[One could also argue that we have a form of this right now (called serial monogamy). Except that if you like another partner, you've got to break up your existing family to make it happen.]
The real other form that exists right now (for some guys) is the girlfriend in San Francisco, the girlfriend in LA and the girlfriend in Reno (not necessarily with any bad premarital sex going on). The breaking up part isn't very fair or nice to someone you may want to be friends with forever.
[Of course, even if this were possible, you'd still have to talk your first wife into it. While that could be tough, it might not be if your wife would rather have you bothering someone other than her for sex.]
And this is where I lose you. If your first wife is someone that you *want* to bother all the time for sex...then you are a lucky man! No need for the second wife.
guess before 1968...that actually was the case. Wow! I think I remember reading about that in a history book somewhere
Being 40ish, I wouldn't know how easy/hard it was to get sex back then either. I guess it was doable, but casual sex ("hooking up") was no doubt much rarer than it is today. However, because such a high percentage of people got married back then, the idea was to get a decent woman before they were all "taken". I got married in the late 80s. Part of my motivation was years of dating subpar, neurotic women. When I finally found someone that was smart, beautiful, and sane, I snapped her up.
While one certainly can have girlfriends on the side, I would guess that can only go on so long before they want a commitment. That gets back into the "getting the milk for free" comment. I think feminism has duped many women from acting in their own self interest. Women have about a 15 year shelf life, approx 18-33. After that, their chances of getting married go down drastically. Given that, it's pretty stupid for them to waste time on guys who won't commit. I went out with a girl for 6 months who I thought was pretty dumb, but she dropped me cause she sensed I wasn't serious (which was true). That was a pretty smart move on her part.
With regard to the last part, people do lose interest in sex. Unfortunately, my wife isn't nearly as eager today as when she was in her 20s. However, my drive hasn't diminished. It's kind of a mismatch and she looks at sex like just another chore. Sometimes I get the feeling she'd be happier farming the chore out to someone else. For this reason, after you turn 40, you really start to see the wisdom of marrying someone who is 10+ years younger than you. [Ah, the joy of annonymity]