I don't intend on having children and don't expect every modern female to either. If they want to pursue their career or dreams of becoming a world famous bodybuilder then who are we to judge?
That said, take the likes of Amanda Doherty as an example, has a number of children and still balances her physique career on the other hand.
Why should raising a family be their one and only role? Once a child is past say 6, 12 or 18 months, why can't the father be the primary carer of the child?
In this modern age, I wouldn't say most women are actually prepared to start a family at a young age anyway, so what is the harm in competing in a few competitions, bodybuilding or otherwise, until they are ready?