The cool part here is that this is solely your opinion. You see not having children as selfish. I see it as just another life choice in a long list of life choices everyone can make. There's no selfishness in living life how you want to live it. I don't like babies/toddlers. At no point in my life have I ever wanted one. Do I owe America one? **** no, I don't.
Anyone that thinks people "owe" or "need to contribute" a child to society has a very dumb, narrow minded view on things.
Society relies upon people contributing to it. If people decide to stop contributing it at best fails to live up to what it should be doing and at worst falls.