For years they told us that the ouside disconnect was for the safety of the fire department and that seemed a good enough reason to me.
It does make it quite a bit safer for a firefighter to just open a panel a shut off a main than it would be to try to pull the meter, cut the triplex, or work their way thru a burning house to locate the main and kill power. Personally I prefer an outside main in the event of an emergency, or at the very least an interior main that would be very easy to reach/get to- it's kind of like a having an easily accessible and "valve ready" crescent wrench dedicated for quick emergency shut off at a gas meter ( IMO, something everyone who has ng needs to learn how to do.) -you may never need to hot foot it to disconnect anything, but at least it's there if something
does happen. Of course tripping a main, pulling the meter, or cutting wires will not always guarantee power will completely off- occupants get awfully ingenious.