I was thinking it would be nice to be able to create an instance parameter to turn on/off graphics in a given tag. Create one tag, place many and toggle on and off various parts. Revit says, "No, sorry Steve you can't do that."
Tags require us to create Types. The yes/no parameters turned on/off in each type as required. Then place a tag type that shows what you want to see or switch to a different type.
Making it possible to use instance parameters is a pretty common request, even reasonable perhaps. However, doing so would mean we couldn't trust that a given tag and type would be displaying all the information it is supposed to show without visiting each and every tag to verify.
Thus far that risk seems to have justified locking it down to only type based tag behavior.