I have to say I agree with you.
When the kid falls asleep in the back seat, and Mom is busy with a million things, she can easily forget the kid is there. It’s almost Christmas; she needs to get to the stores before they close; the store selling Auntie Sue’s favorite bubble bath is on the opposite end of the mall from the store selling a new power drill for Dad; all these people are getting on her nerves... and the quiet baby in the back seat doesn’t even enter her thoughts.
My son always rode in the front seat.
I seem to recall that some cars are starting to have alarm systems put in place to warn of objects (like children) left in the back seat. That might help.
I have heard repeatedly that one foolproof way to prevent leaving your child in the back seat is to put your purse or briefcase (something that you will need) in the backseat. That way, even if you do forget it, you will hopefully quickly realize you left something even more important in the car.