This is why it's better to keep your hammer above the visor. If you ever need it then it's right there. There isn't anything more secure than a visor. I do like to keep an anvil sitting in the back seat though, just in case I need the hammer.
You might think people are not stupid enough to keep a hammer on their dashboard but some people do.
I've seen people who keep those glass breaker hammers in their cup holder, unfastened.
Imagine getting hit in the face by that thing during a rollover at 50 mph.
Or people who have a big metal toolbox on the passenger seat.