Sacrifice was the key. Consider the many versions of Madame X. Ruth Chatterton/Gladys George/Lana Turner did drugs and booze and committed homicide. But it was okay: dying of a broken heart rather than allowing their sons to suffer public humilation redeemed them - they had not failed at their most important job.
Or consider Bette Davis and Olivia de Havilland in The Old Maid and To Each His Own. They transgressed against womanhood by having children out of wedlock. Forgiveness came because they stood aside and suffered as others raised their babies. In Stella Dallas, low-class Barbara Stanwyck got to keep her daughter, but knew to vanish when the little dear hit marriageable age. Mommy never made the wedding pictures, content to watch from the pavement, in the pouring rain, through a (sob]) misty window . . .
Come the 1990 Bette Midler remake, this scene was pulling laughs, not jerking tears. Times had changed and the old tricks - and the old traps - didn't work anymore.
New traps were obviously needed. Mrs Doubtfire (above) provides one, putting Robin Williams in the sort of neuter-drag once favoured by Andy Hardy's mater, all the better to contrast this icon of warmth and nurturing with uptight career woman Sally Field. The subtext being that if she does a man's job, then a man will do her's - and, being a man, will do it better. Or, to put it another way, sacrifice or be sacrificed . . .