I can understand coin and comic book grading because valuation in these hobbies is truly grade driven, plus there is a huge risk of undisclosed restoration.
However, with autographs, it is authentic or it is not, and "grade" should be obvious. If it is faded or smeared it is less desirable than a bold signature. Pretty simple. My sense is only the most slavish really give a whit if a grading company says it is a 7 versus an 8, etc.
I suspect the end game of the grading component is to eventually build online competitive "registries" like they have with graded comics and coins. Users can build sets and get assigned points based of the grade of their items. The users with the highest scores get bragging rights.
I can see it now:
My 27 Yankees set are all 8 or better and I get a "badge" for set of the year!
The registry building is just another way to create an online community of loyal brand ambassadors who all play in the company-provided playground. I don't care for it, but it is pretty savvy marketing.
Maybe it won't take off with autographs, but it certainly has with coins and comics.