Fire Investigations when not performed Arsons go unprosecuted and valuable data is lost.

Believe it or not everyday in the US Fires are not Investigated.
In many states if there is not significant property damage, injury or death  it is at the discretion of the Fire Chief to call for a Fire Marshal or  County or State  Investigator .
 So that home or barn or small apartment house or small business will never be investigated unless its insured and the Insurance company decides to send an investigator instead of immediately settling a small dollar claim.
So What rings the bell it all depends some times its anything over $100,000. but even then some are never followed thru on and with this knowledge an Arsonist could well be at work and no one knows it because no one has checked the fire scene because everything from what the chief sees looks legit.
It is actually amazing how many places have no Fire Insurance in Particular  small business places.
The unfortunate part of these small fires not being investigated is that much can be learned from these fires  to help better determine how fires develop into massive fires .
Since many fires can not be  brought to an absolute conclusion of what caused them  and even fires which have conclusions are often done so with questions if they have actually  been accurately determined . Such as the Ringling's Brothers Circus fire, Lady of the Angels School fire  in Chicago   etc. Where people later come forward to claim they set the fire. But are dismissed as kooks all too easy as time has passed.
This makes all the more reason  the case to investigate all fires in a proper scientific manner .
but costs are always cited as why it is not done .
All too often fire investigations end up pushed thru and evidence missed or ignored and the type of investigation you get depends on the investigators training which is sorely lacking in many cases as investigators are pushed more and more to do more with less.
And Arsonists know this thats why they can often work with impunity knowing they will never be discovered because when fires are not investigated patterns are never put together and 
Arson can be pulled off all too easy .

When its an old structure  like an apartment building with bad wiring and heating systems etc. and under insured to replace the structure .  it is all too easy to just say yea it started down in that basement electrical room because the wiring was faulty and caused it with no conclusive proof because the arson dog got no hit for flammables and there was no sign of break in .   But 
It could have been an easily set fire using just paper and matches  or using a non detectable flammable and unless tenants have been checked out to see if one of them had a grudge against the land lord or  tenant them self was the target of an outside party or even the land lord them self causing it   the fire will go with out full investigation  .The land lord gets his insurance pay out and building is knocked down and not replaced and the perfect crime is committed.

If fires ruled arson are later determined not to be arson and suspects have been released its just as easy to rule a fire as electrical or other cause and it was in fact an arson fire.

and its all the little fires not investigated for there clues how they started which helps stop arson s defective products etc cold in there tracks, before lives and property are lost. But since small fires are deemed not worth it all the valuable data from them is lost.