Well mainly Indigo 3 is integrating the material creation process (File > New Material loads the material preview scene optionally). Add stable material editors in exporters on top and the standalone app was discontinued, end of story.
But I'm making this up really, I did not take part in the related choices. Uneducated guess that is.
Yeah, that makes sense. I was just looking to quickly mock up some materials without starting a new scene
Blender doesn't have a built-in material preview yet but I guess that will come eventually.