Is that because a fire extinguisher is spoken or that it's not essential?

A fire extinguisher will not get you out. A fire extinguisher it to clear a path so you can get to the path outside. Many people get this wrong - they put the fire extinguisher by the door, but if you are at the door you should be going outside not trying to fight the fire. (most fires are small enough that you can put them out with a fire extinguisher so this seems to work - but that is not the primary purpose)

What you need is a path out when there is a large fire. Both exits and fire extinguishers are part of that. Everything else is a nice to have (sometimes very nice), but you still have to prepare for when everything else fails.