Extinguishers aren't for life safety puproses as we all know. But the Government of the day placed a duty on organisations to mitigate the effects of fire.
There are wider issues behind why they have done that, envrionmental, economical, political and social issues to name a few, which are pointless discussing here, as I assume everyone understands what those issues are.
There is an expectation that you prevent a small fire turning into a big one.
How do you do that? you can either train a percentage of your staff on the safe use of fire extinguishers, who then safely attempt to put out a small fire within the limits of their training
Or you could possibly put in fire supression or spinklers systems, or fire seperation as measures to mitigate the effects of fire in some circumstances.
So do you always need fire extinguishers to mitigate the effects of fire? No. But be sure in your FRA to demonstrate there are other measures in place to mitigate the effects of fire if you do recommend the removal of fire extinguishers.
I said before that the mitigating the effects of fire is going to become a big issue in future, and I think you will see more and more organisations prosecuted or have some of formal enforcement action against them for not doing so. There is political will behind it.