There are some grounds to assume that a cognitive dissonance is involved in feeling that children are more a satisfaction than a nuisance. Why do people bother with parenting? It is time consuming, exhausting, strains otherwise pleasurable and tranquil relationships to their limits. Still, humanity keeps at it: breeding.
It is the easiest to resort to Nature. After all, all living species breed and most of them parent. We are, all taken into consideration, animals and, therefore, subject to the same instinctive behaviour patterns. There is no point in looking for a reason: survival itself (whether of the gene pool or, on a higher level, of the species) is at stake. Breeding is a transport mechanism: handing the precious cargo of genetics down generations of "organic containers".
But this is a reductionist view, which both ignores epistemological and emotional realities
