I would have to respond by saying that your assessment is, in many ways, oversimplistic.

You base your assessment of marital benefit on one measure: sexual fulfilment or, as you label it "sex starvation."

Citing, in your personal experience, that women's libido diminishes in middle age. and that "most of the guys (you) know are sex-starved" your thesis is that marital satisfaction is based wholly on sexual fulfilment.

Let's note that a significant number of men have difficulty reaching and maintaining satisfactory erection in middle age (hence the flood of erectile dysfunction drugs on the market), which is likely to pair with their partner's diminished desire. After all, who seeks a flaccid penis?

Or, as likely, who has the energy for sex after working a full-time career, maintaining a home and acting as the sole parent, as we've seen is the case in many marital arrangements?

It's well documented that married women do even more housework than their single counterparts, after all.

https://fortune.com/2019/05/08/married-single-moms-housework/#:~:text=But%20married%20women%20actually%20do,and%20University%20of%20Southern%20California.

Look instead at these numbers for your guide:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4018193/table/T2/?report=objectonly

A fuller picture of the spectrum of happiness.

Translation? If a man is only in it for sex, he got married for the wrong reason in the first place, and would be better off as a serial monogamist or just a playboy anyway. Why bother to put a ring on it if all he wanted to do was get laid?