There are two answers to this:
1. I think it is important to identify a fixture (symbol) by its shape on the plot and to match that shape in the key. I can imagine picking a different key symbol for a plot in the front view than for a plot in the top view. A possibility could be to offer all three possible configurations in the Symbol key -> Appearance -> Symbol configuration ... So the top, side, and front view of a fixture should be selectable depending on your needs as one, two, or three symbols per line.
2. If the symbols are universally usable there is less of a problem. But at the moment there a lot of fixtures that are using very old USITT symbols. Modern LED softlights are represented by an icon of a 10" Scoop from the 1960's. That means that they are hardly recognisable if you do not look at the key. If this is imporoved there might be less need for the multiple views of the same fixture.