By my observation humans enter relationships for a wide variety of reasons, each with a unique set of prioritys.
What is most baffling to me at times is the importance of sex and at the same time a conflicting priority of monogamy- especially among individuals whos sexual appetite vary to a great degree outside of their mate.
I see example upon example of mutually beneficial relationships get torn apart by monogamy. Entire castles crumbling to the ground because sex has had such a high priority (the highest?) and at the same time been shelved to the category with the least amount of freedom.
I'm convinced at this point that it is largely a social/cultural issue. Some value is placed upon monogamy, with statments such as "staying honest" or "remaining loyal" forging those values.
Those that take a different tact, not remaining monogamous, are degraded, thought lesser of.
This in itself is hypocrisy.
Under no circumstance have I ever witnessed monogamy (having been monogamous myself in a long term relationship, even) actually be anything aside from a cheap ploy. Take the stereotypical husband drooling over another woman and his own wife slapping him for staring. So he goes home and masterbates while thinking about her, while his wife does the same thing over some other guy she found cute. Yet they are loyal to each other?
This culture isn't going anywhere, it is definitely here to stay for a long time-- with religious backing it is insurrmountable to try and change it.
But-- peoples relationships? Those are not here to stay. Not if they balance on this concept. Those who are monogamous and think this is a strength are in fact wrong, it is a weakness, their weakness. As the saying goes, the proof is in the pudding- how will their relationship stand up to one member finding the other "cheating" ?
Real strength IMO is being able to love beyond a concept as simple (or complicated) as sex.
As we see people listening more to their own thoughts, being more selfish (is that a bad thing?), and be less interested in a relationship-for-the-sake-of-a-relations
Thus is my theory on why dirvorce rates are at a constantly growing all time high.