The best way to get their attention for something like this, particularly since competing platforms do have backup options, is to post the question in a friendly way on one of the marketing channels, like Facebook or Twitter. Just ask if they’re going to add a backup/restore utility like a named competitor has. At least, marketing staff will read it, and that sometimes moves things.
But my own guess (purely a guess) is that they can’t do this because of the fact that they can, and do change the cloud platform without notice. And smartthings is still largely a cloud-based system, even in the world of edge drivers.
Here’s the official schematic for the new architecture:
Otherwise, you could end up restoring your hub to a version that was incompatible with the most current cloud, and everything would stop working and support would have no way to help you other than having you mail in your hub, and we all know how popular that would be. 
So that’s my guess. Because people have been asking for backup/restore since at least 2014 and it just hasn’t happened.