Putting aside whatever "true sustainability" means, it's unlikely that it's a money thing. It's probably more related to the efficiency of individuals in organizations as they grow, and Apple is already quite large.
It is absolutely a money thing. If Apple didn't have to worry about the commercialization of MacOS, then they could publish the driver code so Windows and Linux clients could offer support theoretically "forever".
They do not publish the drivers though, which means groups like Asahi have to waste their life-hours reverse-engineering for sustainability purposes.
They do not publish the drivers though, which means groups like Asahi have to waste their life-hours reverse-engineering for sustainability purposes.