If you'd like to be less unnecessarily cynical, you can instead read it as "there's someone in the vehicle who is more fragile, and less likely to survive an accident."
I’d like to see it like that too but we don’t observe much « oldie inside » stickers. I don’t think he’s cynical and understand the sticker as a polite way to say the driver have more care for his baby than others human being, which is not to blame of course.
