If you were a parent and opened your child's bedroom door to find them getting intimate with someone of the opposite sex, how would you react?
A boy's parents would immediately smile and close the door, secretly rejoicing: Thank God, my son likes girls. As long as he didn't get her "in trouble," they generally wouldn't reprimand him.
A girl's parents—especially her father—would first want to beat that brat to death. But since murder was against the law, he could only give the boy a brutal lesson instead.
Once that little hippie had been driven away, Dad would begin to worry. His daughter had grown up. She was no longer his precious little girl in a fluffy dress who said she would marry him when she grew up. Disappointment, helplessness, and jealousy gnawed at the old father's heart.
Draco Malfoy was fortunate that Astoria's father had died long ago. Otherwise, with their family's habit of "having the child before holding the wedding," Mr. Greengrass would have challenged Lucius to a duel.
The Greengrass family were aristocrats, but fallen ones, while the Malfoy family had gold coins to spare. There were strong political considerations behind the marriage between their two families.
When Lucius Malfoy had fallen on hard times, the Greengrass family had been his lifeline. Now that life had improved a little, he had begun reverting to his old ways.
When a man married a woman, the woman took the boy away from his mother. Pomona did not dare guess what Narcissa was thinking at that moment.
In any case, Astoria was in an absolutely weaker position in this marriage. If Draco did not stand by her, she would be very unfortunate. Add her blood curse to the mix, and it would be even worse.
For now, the two of