QFT. Hallways, rooms, and boats (in particular) are all wider in tactical gaming than in real life, to make life easier for people moving little figures around a grid.Because squares are 5 feet, and two characters aren’t allowed to occupy the same square for more than 6 seconds. Having to walk single-file down hallways would be a pain.
Exactly this.I'd always assumed because the default indoor scale was 1" = 10' so when you sit down with your graph paper to design a dungeon you use 10' as the unit, and it's most convenient to draw rooms & corridors along the lines.
First time I saw it was 3e, though late-era 2e might have done it also. A few outlier modules from 1e used 5' squares, and there's one (in Dungeon mag. I think?) that had my DM swearing a blue streak until he finally realized the written descriptions only made sense if the map was seen as having 7-and-a-half foot squares!1" = 5' has always been much closer to the nominal 25mm (more like 30+) scale D&D figures have always used. Was it 3e or late 2e that finally got around to adopting that?