The story that the facades on Main Street tell is definitely more subtle that the story told by the "residents" of Carsland as the proprietors there have a much deeper back story, but also the structures in Carsland are more clearly separated by the use of space.
While Main Street is one of my favorite lands, I don't like the recent changes in HKDL, and the changes to the Carnation Cafe in Disneyland as you lose the "empty space" between buildings on the small side streets. Even old turn of the century Main Streets probably had small lots, and little corners that weren't much besides some wooden fences.
If more space is needed for a shop, it actually make more sense, at least in my mind, to expand the street back as that would draw more people to the shop as there is more to see visually, rather than trying to draw in more people by bringing the shop closer to the curb.
I can see why Walt wanted to build a haunted house off of Main Street, what a perfect setup for that type of attraction as Main Street is almost "too busy" with shops and people everywhere, and then down a twisty side street sits a hill with a haunted house. Even though WDI wouldn't do this in Disneyland, it would be nice to have open space leading off of Main Street, maybe to a small little park and a shop. If you watch "So Dear to My Heart" there is a more open Main Street, if I recall, and having that feel in the park would be great. Having the side streets open and uncluttered is important as it breaks up the blocks of buildings into somethng more appealing, without them, you've just got a long street with a monotonous row of buildings, which can feel claustrophobic.
Here a little more about the Haunted House on Main Street,
http://www.doombuggies.com/history1.php