Product of the times. It used to be that infidelity was uncommon, but it happens with around 35% of unmarrived couples and around 20% of married couples today, with twice as many being the mens’ fault, probably due to their own faults not being the men that women deserve.

Around 65% of romantic couples begin as platonic couples.

The best relationships are based on a foundation as best friends. If you can’t be best friends, then you can’t have a strong enough relationship to make marriage work. There are a lot of people who get married based on expectations and poor reasoning, but the relationships that last are between people who are best friends, can communicate effectively, and naturally meet each other’s needs last the longest. That is a narrow band of people per individual which can persist without outside pressure(culture, religion, kids, etc.).

We are so lonely and desperate to have someone to love and be loved by that we end up in relationships that are unsustainable. Meeting someone who actually completes you, or feels more compatible, ruins a workable relationship because it is not harder than the easiest day spent with another person who can only temporarily satisfy the needs left unfulfilled by a relationship with a viable partner.

The grass is always greener, but your grass can be just as green if you put in the work, and that takes effort that may not seem as cheap as hopping the fence. Put in the work and the hassle of switching pasture will be less than the upkeep, that is hard to understand.