It's a big job for anyone, and even though we are a highly intelligent species that can see the importance of propagation, there must be moments when the haze of affection clears from a parent's eyes and he or she is tempted to pad a wicker basket and find the closest river.
Fortunately, nature's never willing to rely on the off chance that anyone will actually like their child. Through years of evolution, it has hidden elaborate fail-safes in our brains to ensure that we won't abandon our young. "But Soren," you harried and sleepless parents will cry in a voice just soft enough not to wake your tiny beast, "You have no children -- what makes you think you know anything about raising a kid?" Well, you just answered your own question, Jack; only the childless can objectively see the spell you're under, a spell that's meant to look and feel a lot like love.