The application calls it "Seating Device Comprising a Forward-Foldable Backrest," but I like my name better.
The inventor describes the alleged motivation thusly (my annotations below):
[T]o increase the number of cabin seats [and thus profit], the space allotted to each passenger must be reduced.
However, this reduced comfort remains tolerable for the passengers  in as much [sic] as the flight lasts only one or a few hours. 
According to a first solution … , it is possible to reduce the seating width allotted to each passenger in order to place an additional seat in the width of the cabin.
This first solution has already been pursued, and it is now no longer possible to further reduce the seating width, particularly in economy class. 
According to a second solution … , it is possible to reduce the distance available between two seats, that is to say the distance needed for the legs of the passenger.
This second solution has also been pursued hitherto, and it is difficult to continue to further reduce this distance between the seats because of the increase in the average size of the passengers. 
According to a third solution …, the design of the seats has to be optimized so that they present the smallest possible bulk.
 The passengers themselves might feel differently about this. Did you ask any?
 The difference between one and "a few" hours on a bicycle seat can be pretty dramatic, my friend. And do your lawyers know you don't think the difference between one and "a few" hours is significant?
 Translation: Americans are getting wider, not narrower.
 Same as above, but thanks for suggesting that the main problem is that our legs are getting longer. You're very kind.