Usually, you need to think about babyproofing your house once your child reaches a certain age. You’ll have to purchase baby gates and cupboard catches, to keep your little one’s grasping fingers from being squished while they’re exploring.
A playpen is also quite a good idea if you have areas in your house that are a little bit more dangerous. Usually, however, you’ll put the baby in the playpen, where they’ll play, safely. In this case, dad obviously thought he might be able to use the playpen to get some peace and quiet of his own. The focus is on keeping his computer safe, rather than the baby.