You can't always predict that after you put out the chimney fire in the wood stove or fireplace that the fire's out. In the case of my former abode, the fire took hold where the duct went through the ceiling of the 1st floor & got into the subflooring of the 2nd floor. It didn't break out for about six hours (at least that's when the fire department was called when a neighbor noticed flames). If it's a chimney fire, it can go through the cracks created from the chimney fire, into the wood frame of the house--and around here, wood in old houses are tinder-dry--and have the fire smolder for hours before getting enough head on it (or to a good oxygen source) so that just dousing the fire with a garden hose isn't going to cut it.
Then there's the matter of smoke inhalation. I've had it once and it's not something I'd go through again, and I was young & healthy (although I was pregnant) when I caught a big snootful of smoke. If someone has any respiratory or heart problems, it is definitely risky.