Appreciate that point that they are competing for time (as I was only thinking of monopolies over content).
If the reason it isn’t used is that users don’t “trust that the system will give what they want given a single short description”, then part of the research agenda for aligned recommender systems is not just producing systems that are aligned, but systems where their users have a greater degree of justified trust that they are aligned (placing more emphasis on the user’s experience of interacting with the system). Some of this research could potentially take place with existing classification-based filters.
Agreed that’s an important distinction. I just assumed that if you make an aligned system, it will become trusted by users, but that’s not at all obvious.