I think what denadog was trying to say is that while the incidence of confirmed structure fires are way down, the importance of a timely response when that emergency does occur is still just as important. We have no way to predict when and where these fires will occur.
When we arrive onscene, we're absolutely going to do a primary search, unless everyone is reported to be out of the house, and also accounted for. This is our mandate. What we do before going in is look at the conditions, and determine if an area of the structure is tenable before committing to a search. Obviously if a room or floor is fully charged with thick smoke for a while, or if the thermal imager shows oven like temps, no one unprotected could possibly be viable, so we wouldn't search that area. Obviously if most or all of the house is engulfed, we're not going to search. If it's newer construction, and it's the fire has spread through the void spaces, it will fail soon, so we're not going to make an interior attack. On the same token, a home can be fully charged with smoke, and the fire can be little more than a room and contents (not affecting the structural members, thus no immediate threat of building collapse).
Basically, if there is the chance of a victim being insidee, and the conditions are such that the victim could still be viable, we have to risk our own necks to search. If the conditions are untenable, the victim will be dead anyway, and we can write them off.
Also, if we're working a fully involved garden apartment or townhome unit, hitting it with master streams (large GPM exterior lines), and going inside to mop up (even spraying from the doorway then treading carefully), we can save all the exposures on either side.
Here's an example of a flashover while crews were making an interior attack, with a report of a possible trapped occupant:
http://www.youtube.com/watch?v=30SCtOHUGhc
This was a couple of minutes after entry. The room can flash quickly. It can look okay one minute, and be going off the next. It happens that fast. The Truck company was upstairs searching, and they were okay. E422 were pulled out from the front entryway by R426. Everyone was okay. We have really good gear. No burns on this one. We also saved the row by containing the fire to the end unit, BTW.