I think people have children for all manner of reasons- sometimes out of a pure desire to nurture and witness life, sometimes out of an absence of choice, sometimes in order to hold on to a partner or create an heir, sometimes without thinking about it in any particular way. Not all the reasons to have children are the same, and not all of them are necessarily unselfish. Not all the reasons not to have children are the same, either, though. Not are all those reasons necessarily selfish.