I am not in the industry, but I do keep and eye and ear in this area, as I am having a 1925 Mason & Hamlin RBB restored. I know that these types of reproducing pianos have a small following among collectors, AMICA was mentioned. It's primarily due to the expense of rebuilding and who actually does the work. Good re-builders of these pianos are becoming a rare commodity, and when you do find one, they are often booked 2-3 years in advance. To add another 6-10K to rebuild the player mechanism is a lot when you are also paying to rebuild the rest of the piano.....add to that, the cost of the rolls, storage considerations as well as the fragilty of the paper from age/wear and tear. Also, with the advent of the electronic piano and the solenoid systems such as Disklavier, PianoDisc, with remote control etc., the reproducing piano, Ampico, Duo-Art, Welte, which btw, cannot record by themselves, seem outdated..... but not to collectors.
Another factor is the music selections...most of the reproducing rolls are either classical or popular hits of the day, 1920-40's. With the modern solenoid systems etc. you can have up to date music and you can also record and playback your handiwork with a remote control. I think these are some of the main reasons why you are seeing a decline.