Marriage can also involve growing into each other, like a tree with a split trunk twining round itself. Neiither marriage in the movie worked like this, though - I think because both men were committed other than to their wives and both women eventaully developed other interests, Alma in the job and in monroe, Lureen in the nusiness and making money. Hardly surprising when you think what they were up against. Lureen just didn't have any reason to divorce Jack - she evidently wasn't interested in anyone else and I can imagine them going on, progressively less and less involved in each other's life, without any impetus strong enough to part them.