Maybe Lego needs to manufacture sets that are just "collections of bricks". In fact, I think they did that at least for a while. I know my past self would have loved to have a few sets that when put together would provide the kinds and variety of pieces used in books such as The Lego Play Book.

They still do that. I can go to the store right this very moment and get a bin of bricks. There's no problem here: people who want designed sets can get those, and people who want just bricks to use as building material can get those.