Hoist high the flag! We've declared war on realism in a fantasy game! Again!
Noisms has a post about the absurdity of trying to be realistic in a fantasy game. The argument goes: why look to medieval documents for details of medieval economics or practices when medieval Europe didn't have dragons, elves, goblins or magic? Any of these, had they been real, would have changed the way people did things. The example given is the way cattle or sheep are managed; if dragons or griffons existed, farmers wouldn't have kept their animals in uncovered pastures.
Except, of course, that medieval Europeans *did* believe in all those things. So why didn't that affect the way they did things?
The problem, here, is that there's a disconnect between how D&D (or other fantasy games) portray magic and fantastic creatures and how medieval people thought about magic and fantastic creatures. Fantastic creatures were believed to be extremely rare, sometimes even unique. There weren't flocks of gryphons or herds of unicorn; generally, there was only one in a very large area, perhaps only one in the entire world. And they often didn't seem to obey biology. We often worry about the ecology of fantastic monsters (that gryphon needs something to eat,) but medieval descriptions seem to suggest that these creatures eat only out of spite, not necessity.
And that leads to something important: it's not the attempt to inject realism into a game that is absurd, but the fetishism of realism and application of a scientific world-view to a fantasy game.
There's actually a good reason to look at things like the Domesday Book: to find a frame of reference. The GM and the players generally have a good idea about things like how fire works, how climbing works, how throwing things work, and other basic actions. Not a thorough knowledge, as a physicist or mountaineer or champion knife thrower might have, but enough to come up with plans like "let's tie a spike to the end of this rope and throw it like a grappling hook." We have a frame of reference. Some other things, we don't have a frame of reference for. Most of us are city people and don't farm, or at least never farmed in the Middle Ages; we don't know what they might own, or how they do things. The same applies to castles, medieval trade, and many other things.
So, we might read up on some topics to get a better grasp of what things would look like. And we might run numbers -- not during play, of course, unless we're obsessive idiots -- to get a better feel of what the population might look like or what items might be in a treasure trove.
The problem is that some of us *are* obsessive idiots, and fetishize the numbers. We -- and by "we", I mean "not me" -- get bent out of shape at the idea of the details not working out right, of there not being enough sheep to support both the local population and the occasional dragon-raid. And so, we bog the game down with tedious number-crunching and arguments about how much a dragon would realistically consume. I believe that's what Noisms is really complaining about; not the act of comparing our fantasy to a real-world example, but the madness that causes some people to forget what we're playing the game for.