Flopsymopsycottontailbuns I understand the point you are making but then what constitutes as an 'acceptable' reason to decide not to have children?
I think citing a career is a very valid reason to decide against having children (tbh I think any reason or lack thereof is a valid reason.)
Cost of childcare is extortionate - many parents either give up work altogether thus stalling their career progression or work at a net loss to maintain one foot in the door.
If a parent doesn't have external support - guess who nursery or school will be calling if the child feels ill. That's right; how patient can an employer be if a member of staff is having to leave work to collect their child or ferry them to appointments etc with little to no warning.
You're right that no-one is irreplaceable but I'd wager that indirectly (or even directly) many women have felt themselves being slowly pushed out or sidelined because their priorities rightly lie with their child and not finishing off some report or presentation for a client.
How productive do you think someone can be at work when they're experiencing night after night of broken sleep due to being up with their dc?
Parents have to negotiate school holidays. Where will the dc be during the Easter holidays, half terms, Summer holidays? Activities cost a lot of money and your typical 30-day annual leave allowance won't cover the entire academic year.
Of course for some parents having children doesn't negatively impact on their careers or jobs but I reckon for the vast majority it does.
One of my friends doesn't want to have children because she doesn't want to ruin her figure. Horses for courses. That's just a valid choice as much as any.