duty

"Be fruitful and multiply".  This is the command given to the man and the woman in the garden and recently I was reading through a book that said that this is the best reason we should have children, because God commands us to.  I read this and it just rubbed me the wrong way.  I've been trying to discern whether it is because I just don't like being told what to do (especially since it begins with something called "labor") or is there something else?