That's a very narrow view that's a function of one's religion, culture, and values.
When I was in school, (US) my very Catholic French teacher explained that his uncle, in France, had a mistress. His uncle's wife knew and was okay with it. What my teacher was explaining is that the culture around marriage varies considerably through the world, and you can't take for granted that what we were taught (monogamy) is the standard that others live to, or even expect from you.
Please don't make the mistake of assuming that American culture is homogeneous: It's not.
Perhaps it’s you that is out of touch?
Both partners in this case know and/or participate, you don’t want drama at your games night after all. There is no wrong here, it turns out that many partners like seeing their partner have a great time.
That’s not quite true. A more accurate statement would be: A marriage may be annulled in some U.S. states if one spouse entered the marriage with a concealed, permanent intention not to consummate it, and that intention constitutes fraud going to the essence of the marriage.
If the couple was having sex after marriage, and then one partner decided to cease having it some time later, that is generally not grounds for annulment.
If it were permitted, this would make many, if not most, late-stage marriages subject to annulment. People get sick and injured or just incapable in old age.
Well we don't know that, you are not legally required to love someone you are married to and I have no clue what their relationship is like or whether they have any sort of "arrangements". I could hardly care less really since its their private matter.
> just what might he do to you, the customer or shareholder?
I don't really see a correlation between those things. All sorts of immoral degenerates (e.g. Musk, (potentially) Gates and I assume plenty of other lesser known CEOs) have generated massive amounts of value for their shareholders.