From what I've read, it often happens when there has been a change in the parents' routine. For example, one parent normally takes the child to daycare, but then one day, the other parent is supposed to take them. Then that parent is just following their normal routine (which doesn't normally include dropping the kid off at daycare) and just drives on to work and forgets about the child. And it usually happens with babies/very young kids who are likely to fall asleep and not make any noise to remind the parent that they're in the back seat. But still, it does seem crazy to just forget your child. I could maybe see making that mistake and leaving them in the car for a few minutes...but it seems like eventually, you'd think about your child and realize that you had never dropped them off or taken them out of the car. In a lot of these cases, the parent didn't even realize what they had done all day long and found the child dead hours later.