Earlier quoted context omitted.
I have no doubt this is a widespread behavior, but I do have doubts as to whether or not this benefits children. Children seem to benefit primarily from watching relationships that genuinely make both parents happy. There's very little evidence to support that faking it yields results of children reacting as if you weren't faking it. You might as well divorce.
My friend in high school suffered from depression in part because he was well aware of that fact that his parents were only staying together until he graduated. Despite any attempt to put a rational face on it, he believed his existence was the source of his parents' unhappiness. Another friend of mine is doing this with his wife right now. He's utterly miserable, but the racial stereotype of the missing black father…
At a certain age though the parents should split if it isn't working. It's definitely far easier to deal with your dad or mum leaving if you're 10 years old than if you're 1 year old