And body design, IMO, has very little to do with whether an update is significant or not. I mean, let's say the 6S got rid of the camera bump and antenna lines but there was no 3D Touch, Live Photos and the A9 was just a modest improvement over the A8. Would that be considered a significant update? I think not.
I agree, and yet people are different.
Some emphasize the body design and look for a change there to differentiate models.
Others are looking for specs and features.
To one, the change from the "S" to the next model is significant because the design changes and they can show off the latest and greatest.
For others, they want the "S" as the newest toy with the fastest processor, highest megapixel camera, newest killer feature, etc.
Shrug... in the end, it is mobile device.
It makes calls, takes pictures, sends and receives email, runs Twitter, Facebook, Instagram and some games.
Some people are defined by their car/truck, others by their position/title, some by their country club, college they attended, etc.
In the same way, some are defined by their phone, and it is the most important thing in the world to them.
To each his/her own.