>>That's why you don't rely on your memory, and you always keep your eyes peeled and look around you. Check your car when you get in and out.<<
Yep.
However, not being a computer nor a machine, sometimes accidents happen - and sometimes with deadly results.
That's true- but IMHO there is a difference between an accident that is likely difficult to prevent and one that is entirely preventable by taking some simple precautions.
Kids are resilient but they do fall or choke or otherwise injure themselves because they aren't living in a bubble. But being left in a car isn't that sort of "accident".