The policy of "let some fires burn" has been in practice for a few decades now in our corner of the woods. Ever since the Yellowstone fire in the 80's, we've focused our efforts on containment instead of extinguishment (i.e. make a best effort to keep it away from human settlements); letting land lost to the fires just burn out naturally while stopping them from claiming too much land. Should we let them burn more? Perhaps.
But it's never so easy. The cost of just letting some go when they're a couple dozen or even hundred acres can spiral out of control when you're suddenly attempting to stop a 300,000 acre fire that has already burned out 16 homes and is threatening towns. Yes, firefighters die fighting fires. Civilians also die when an uncontained fire goes from a theoretical threat on the horizon to consuming their house in a matter of minutes.
Fire doesn't respect property boundaries, and can travel a tremendous speeds (upwards of 10mph). And they aren't really like floods - it's not just the forests that burn, it's the flat lands with all the nice dead grasses. Grass fires can move even faster than forest fires, given a wind to push it along.
Humans aren't the only ones affected, either. The livestock which used that land for feed still has to be fed, or face starvation. Argue all you want about the inhumanity of our treatment of livestock generally; letting them starve due to a lack of hay (tied to a lack of money) is worse.
There are some who feel that they should not have to support those affected by natural disasters. I'm sure others will be happy to return the favor.
(300,000 acres ~= 142,000 ha)