Sorry, I can't expalin why. That would be a question for the architect, Lane Williams of Coop 15 Architecture.

It's almost always an aesthetic decision provided we can find ways to incorporate outdoor storage (In this case there's a cedar shed on the left). We wanted to keep that strong horizontal line and place all the vertical emphasis on the 2-story addition, a solid wall with a garage door would have unbalanced that effort.

Here is the initial concept that the architect is proposing. I think we've settled on trying to figure out how to do the garage