The original use cases for these devices, nothing to do with SmartThings, was in the rooms that had three way switches, where you no longer needed the aux to be wired to the master switch because everything was being done wirelessly. So it was easy to dedicate a button on the SC7 for whatever the original aux had done, and then you still had a lot of buttons left to assign to various scenes.
So the original switches were a wired master, a wired aux and a traveler wire between them.
The new set up was a wired network master, a networked aux which drew its power from the mains, but communicated wirelessly with the master, and no need for a traveler wire.
You didn’t lose any functionality, you actually gained a whole lot.
So as always, “all home automation is local.” If you only have one switch controlling the load to the light fixture, then removing switch control of that load wouldn’t make any sense. But if you have two switches both controlling the same light, replacing one of them with the scene controller expands your options.