True, but in those cases people probably do start off with good intentions. It's simply easier than harboring resentment and anger.
Also, it's been argued that the Japanese way of arranged marriage between individuals with similar backgrounds actually works well much of the time - the marriage may not be based on love initially, but love grows in such relationships.
Of course, societal pressure may be the reason that some couples stay together, rather than love.
But, I think that perspective is interesting and perhaps true at least some of the time. Especially given that romantic love so often turns out to be wonderful but short-lived.