Why does our society penalize motherhood?

Over the years I've seen countless pregnancy discrimination cases, despite all the advances we've made in the areas of equality and equity many organizations still feel they possess a carte blanche to terminate the employment of women who are pregnant. Human rights legislation, employment standards, and increasing societal intolerance for pregnancy discrimination have done little to protect women who face this issue head on. 

Despite having a large circle of friends, only a handful have children. Within my generation there seems to be a general reluctance to commit to having children, but it goes beyond that and there seems to be a pervasive idea that one cannot succeed in today's world if one is burdened with children. As much as it pains me to level this analysis, it seems that the perception out there is that child-rearing is a barrier to: careers, further education, and success. 

This is a public policy issue that continues to be unaddressed by politicians, business leaders, and in the media. Take the legal profession for example, at present women are fleeing private practice in droves as it's generally incompatible with having a family, but you can see the trend in the legal profession repeated in many other industries as well. Perhaps it's high time that as a society we stop penalizing motherhood and raising families, it's only natural that people would want to do this. Below I've attached an article and a report from TD Economics, see:

'Motherhood Gap' in wages hits women hard

Career Interrupted: The Economic Impact of Motherhood