Thunder Bolt
Silly old bat
What if the baby ISN'T on board? The Emergency Services could waste precious minutes looking through the wreckage for a non-existent baby. I know for a fact people don't take them down when the baby isn't with them.
Fortunately they've become a lot less ubiquitous in recent years as people have realised they made no difference whatsoever. As usual the Simpsons got it right:
Marge: "Hey look Homer! I got one of those 'Baby on Board' stickers. Now people will stop intentionally ramming us!" I think that shamed quite a few.
What if. What if. That's up to the parents to be responsible. I haven't used one myself, but was posting what I believed their purpose to be.