Motorways were designed to move traffic as fast as possible over long distances.There was no such thing as variable limits or not providing a hard shoulder for breakdowns because that obviously defeats the object.
In general I try to avoid ‘smart motorways’ or in fact most motorways because they are now mostly about moving as much traffic as possible as slowly as possible.
What’s in it for the road user other than the lose lose of possibly being caught up between junctions in a massive unavoidable jam.
There’s no upside in that environment.