Don't think it's a question of ownership, two things seem to be the reasons manufacturers make parts: 1. because they feel that parts availability is part of the quality of the product (which I think is becoming less of an issue in our hobby), and 2. because they can make money on parts.
USAT has consistently had replacement axles in stock, for the last 10 years, so why? Clearly there is profit there.
Aristo had a hard time with parts, and it did not make sense until Lewis Polk shared the information that it was too expensive unless the parts were made at the time of the manufacturer of the main product, and then he was worried that he would have excess parts on the shelves.
There's some famous quotes about Lewis not wanting to have "parts sitting on shelves", which combined with their penchant of shipping all new products out in the first 2 weeks to dealers, having nothing in stock at the Aristo HQ, shows that his business model was don't stock anything, manufacture and sell it out.
Good for profit, bad service for customers.
Unfortunately this attitude is getting more prevalent, irrespective of the demise of Aristo.
Greg 888 (oooh, cool number)