Why babies?

Laura • 30. Currently not TTC.
I'm wondering if any other women question the reason behind having babies. I understand it's lovely to have children & see/feel what it's like to have babies with somebody you love. 
With human emotion aside, what I think about first is that our world is so terribly overpopulated. 
Does anybody ever consider other ways that life can be fulfilling aside from children? I'm 27, very well travelled, educated, lots of friends, love my career, family & partner. I feel like without a baby I could have a wonderful life, I really do. Societal expectations & even my own instinct tell me that I should have babies, but logically I know it's just another person that will be living in the pretty competitive & overpopulated world that we have created. I could be happy either way, how about you?