Show commitment and loyalty (and if you’ve chosen a good guy) then you get commitment and loyalty in return. Show none and invest nothing, you get nothing in return. That’s where we are today.
It happens. Some people are just scumbags. A woman has to assess the character of the man she chooses. For the guys who marry early, have the wife support them as they get established in their career and then dump her once he's successful, I have utterly no problem with the courts giving her at least half the wealth and big fat alimony. She deserves it in that case.