TBH I cant think of a single reason people continue to use spritefont+ in C2 as the native spritefont plugin is better.
you obviously haven't used spritefontplus.
-No need to add loops to go through the JSON file manually for non-monospaced fonts. Instead it's built into the object and has a place for the JSON file in the properties panel
-Once those fields are updated you get to see exactly how the font (spacing) will look in the construct 2 editor (which the native one does NOT do -- in native you have to keep running the game in order to see how it will look and line up etc... creating cumbersome and slow workflow)
those 2 reasons make it extremely valuable. I hope someone makes a C3 version.