If your goal is to save lives, there are other things you can regulate that are orders of magnitude more cost-effective. Where the expected price of each saved life is just millions instead of billions.
When there was another discussion on this topic a while ago, I spent some time reading about fire deaths in Finland. Finland is a country with more fire deaths per capita than most Western countries. Partly due to attitudes, and partly because of the prevalence of saunas, which are almost as big fire hazards as kitchens.
What I found was that fire deaths that could have been prevented by a second staircase are extremely rare. When people die in a fire in an apartment building, it's almost always in the unit the fire started. Either the people didn't notice it quickly enough, or the fire blocked the front door.