The last few times I've flown, I've noticed that with the other 'emergency' gear that the crew has stowed away in one of the overhead bins, they now have a fireproof bag in there too. So it's not quite at every seat, but they do seem to carry some on board.

That does very little for situations where checked-in baggage has a lithium ion battery that ignites. They tell you to remove things like laptops and portable batteries from your checked in luggage, but I haven't heard disposable vapes mentioned, and those very often have lithium ion batteries too.