Part of the problem resides in the culture of downvoting. Oddly, such cultural behaviors are quite different across different SE sites. Even if one does not understand a short answer, I see no reason for downvoting it. In that case, comments are just great to improve the short answer if needed.
As much as a short answer might not be what the OP needed at the time of asking, I believe that when the OP comes back later, or for all readers, a nice short answer is a good complement to longer ones.
To make it short: I believe that, in an ideal world, most comments could be removed without harm after they have been taken into accounts. Comments are scaffolds, to help build a house of questions and answers. Long and detailed answers can be seen as foundations, walls or roofs. A short answer can be stairs, a window, perhaps a piece of decoration, and has its own merit.
Short answers might even be a pretty sketch of the whole building, more informative than the complete blueprint.