If you're an emergency response worker, you're going to have professional equipment including lights specified by your organization and this whole discussion doesn't really apply to you.
D cell incandescents run for 10-20 hours, really they do, and even longer if you use the lower powered bulbs intended for AA's. There's some LED bulbs available for them too, but they're a bit overpriced IMO, even the 5mm ones.
Grocery stores don't stay open for business if it's pitch dark in the store. (The one near me in the NE blackout set up some of those candles in glass jars, which was enough).
If you're in an office building that goes dark and you need to get out, that shouldn't take more than a few minutes, maybe an hour tops in some wreckage situations. In the WTC case, it was about 2 hours from when the planes hit til the buildings collapsed.
For comfort lighting sitting around a house, 5mm LED's are enough, really they are. A 1AA CMG Infinity does the job fine for around 40 hours nonstop on one AA alkaline. An LED candle with two D cells would run for weeks or months.
What does it mean about the world moving to AA's? It doesn't mean you can't get D's any more. They are still easy to find everywhere (of course during the NE blackout, stores sold out of them, but they also sold out of AA's).
During the NE blackout, the Arc AAA in my pocket was really all my family needed, and something like a Photon squeeze light actually would have been enough. We used the AAA as a candle for sitting around talking, but only because we had plenty of batteries on hand, otherwise we would have done fine without that. My mom had a radio/tape player powered by four D cells that we used for news. It ran at least 40 hours on four 25 cent "heavy duty" cells, not even alkalines.
Right now I'm EDC'ing a Countycomm coin light set up with one 2032 cell for 40+ hours of runtime at about 1/10th the brightness of an Arc AAA. Even that's more than enough light to find one's way around a dark home or office. Everyone should have one of those. Brighter lights are important but usually won't need nearly that much runtime.
A lot (not all) of the emergency preparedness thing for many of us seems like a rationalization for our flashaholism. We can be happier about it if we just tell ourselves instead "I buy these flashlights because I like them". Certainly knife collectors who buy decorated Sebenzas and suchlike aren't under many illusions about practicality. There's nothing wrong with appreciating something that's well designed and well made. If you take a photograph that you really like, a really good enlarging and framing job will run you a few hundred bucks minimum, and then it just hangs on the wall doing absolutely nothing except making you happy when you look at it, and yet that's a perfectly valid reason to do it. Flashaholism is the same way.