[Anaraxes]

Partly just to go with that retro nostalgia feel, I think.

But there's no difference between laying out some megahex tiles to make a dungeon room, or putting a hex grid over a rectangular room and saying "but you can't use the fractions of a hex around the edges". No one's seriously suggesting that the rooms are chiseled out of rock with a hexagonal pattern and zig-zaggy walls. (They might be, of course; it's a cultural thing, but probably not.)

But the map is not the terrain. If you can imagine that there's a flat wall there with some little spaces that are mysteriously impenetrable, you can just as easily imagine that that zig-zaggy boundary isn't precisely the edge of room, which actually lies less than a hex beyond. Either case is a representation of reality -- which is this case isn't even real, since we just made up a dungeon in a fictional world of our imagination.

I always wonder why the strict square-grid players don't fret over the fact that every culture builds every one of their buildings with the walls in exact east-west, north-south alignment. Plenty of cultures liked to have their entrances face east, at least in general. But those maps are always laser-straight down the lines of latitude and longitude, every hut an astronomical observatory. Freaky weird coincidence, huh?