I was under the impression that more modern building construction and heating technologies have already made a large percentage of professional firefighters redundant - hence why they spend as much time responding to car accidents and working as EMTs as actually fighting fires.
The number of fires has indeed fallen dramatically. However, until the day when there is zero risk of there being a house fire (and we're a _long_ way from that), you still need to maintain a staffing level that can get the job done.
Last year, London announced plans to let go 10% of its firefighting force. This is despite booming population and construction. In 2004, there were 572,000 fires in the UK. In 2013, there were 193,000 reported fires. (https://www.gov.uk/government/uploads/system/uploads/attachm...)
Sure, when you scale it up to the something the size of a city, then you can say "We want to be able to handle X major incidents at the same time over the entirety of the city."
My point is that X will continue to shrink (as has been the trend for decades), but never hit 0, and you can only consider a limited area before response times become an issue (even if you somehow got to the place where you were very confident there would never be more than one concurrent fire in the UK, obviously you couldn't reduce staffing to a single company).
