Apparently you need that "possum scraper" to hold the license plate in some jurisdictions, if your rear fender/license plate holder doesn't extend far enough to the rear of the bike. I was told by a CHP officer last year that California (at least) requires that an illuminated license plate must be located at the most rear point on the motorcycle. He told me that is why most after-market "fender eliminators" are not legal.
Personally, I am not a fan of the possum scraper. BMW starting installing them on their GS models about 20 years ago, supposedly due to a requirement of the German TUV to control spray from the rear tire so as to not throw debris into the air and onto following vehicles. I can't recall that they ever used that system on any of their road-only models, preferring instead to install (at one time) very long rear fenders that covered the upper portion of the rear tire, when looked at from the rear.
Now it seems like you either get a useless (for water spray protection) license plate support like is used on current Zeros or my BMW RS or, if the motorcycle designer doesn't like long extensions coming off of the rear of the bike, they install the possum scraper.
