I think Hollywood didn't want to be predictable so the endings of movies over the past few decades did not follow the normal 'happy ending.' No, wedding bells, all sorts of endings, but definitely no weddings. They are old, trite and been done before.
However if you ask me, this approach is tiring and old. Movies of long ago ended with the couple getting married and living happily ever after. I miss those endings. Now they end with pregnancies or babies and no marriage, new homes ... with doggies and yet still no marriage, couples in love ... in business together ... in bed together ... yet no marriage. Frankly I think it has become predictable again. I'm not sure but I can't help but think that all those living in sin, in Hollywood can feel less guilty because the masses of movie goers are in on it now ... simply by getting a ticket and sitting in a theater. It eases the natural conscience. But easing the conscience does not make it right. It is still wrong.