I agree on some of your points disillusioned, mainly that:
- Human behavior is, by virtue of a very deep biological imperative, driven to procreate, and usually not monogamously.
- The traditional sanctioned monogamous marriage model has some fairly dismal statistical success
- Our current society is almost pathologically driven to promote an ideal that, at least for many, maybe a majority, will not have great results
However, there are other deep biological imperatives that play into the equation:
- Humans are behaviorally greedy when it comes to resources, which is also a good primitive survival instinct. When extended to relationships, that can lead to a sometimes overwhelming possessive drive that can heartily interfere with a poly lifestyle.
- As a species that owes survival more to intellectual means rather than more primitive methods, we have for better or worse risen to a level where the ability to control our sexual whims separates us from other species.
- That great intellectual superiority we have over other species comes along with a lot of baggage, like insecurity, rational and irrational fear, complex emotional responses and a host of other nuances.
Yes, most long time married couples are not as sexually active as when they first met. There are measurable chemical changes that occur between infatuation (NRE) and long term bonding (My Luvy Soulmate). This does not discount the very real, and most valuable long term bonding, as that cannot be measures with the number of times a couple jumps in the sack.
It is quite understandable that many couples yern for that long term bonding, and seek to protect it against disruptive new influences.
When the danger to that long term bonding is perceived as being too much a risk to dally with new infatuations (NRE), some are quite happy to stay the safe road and remain monogamous. Those fancy, exotic brain chemicals that course through the cortex when we do the mating dance can be *awfully* disruptive, and cause better sense to exit stage left.
Bottom line, it's all a big balancing act, and not everyone falls on the same side of the tightrope. there's really no right or wrong about it.