Portability is definitely not why I write on this scale.
First things first, the main reason you see Sam standing at 4 inches tall is because the majority of my stories are either Brothers Apart, or AUs based on Brothers Apart. The scale is not going to change between them.
Second, I do have other stories that work with different scales. Reversal of Fate and An Ounce Of Courage both use the scale where Sam/Dean stand at 3 inches tall. This scale was discarded for BA because if he’s in it for the long haul, he’s going to need to do things for himself. He is not dependent on Dean in any way as some people seem to assume. Sam survived most of his life without his family around and could easily survive without them. He stays with Dean for reasons all his own.
–Sidenote here: In the horror story, Jacob is reduced down to barely an inch and a half tall and we’ll see exactly why that’s not a good thing. It’s a horror story for a reason.
I also won’t work with the Swift scale (Found in Gulliver’s Travels and The Borrowers). Since I write for enjoyment and I don’t enjoy writing my characters at 6 inches tall, you won’t find that here.
Lastly, the scales I and @neonthewrite use are not 4 inches = 6 feet.
Sam stands 4 inches tall, but his actual height is 6′4″. This gives us a ratio of about 1/19. If we put him and Bowman next to each other, they’re both 4 inches tall. Same scale, right?
Wrong! Bowman is actually the equivalent of 6′2″ in height. So he’s tall, but not quite at Sam’s height. He’s going to be disgruntled if they ever stand at the same scale and he comes to discover this human he can look straight in the eye is actually taller than him. Bowman’s ratio is about 1/18.5.