Also doesn't match the size of doorways in very old houses, or the size of bunks on old sailing ships.
Have a closer look at a uniform worn by the average WW II soldier. A size 40 coat was large.
There are other explanations. Small doors are easier to defend and weatherproof. Space on ships is always at a premium. Check out bunks in a modern sub. You see similar arguments because the beds are small, but period illuminations show people sleeping in a reclined position, like a chaise lounge.