There's different categories of what you call "specialized" pieces though. Some only make sense in a specific set (e.g. a light saber piece in a Star Wars set),

There's different categories of what you call "specialized" pieces though. Some only make sense in a specific set (e.g. a light saber piece in a Star Wars set), and some are completely generic but only exist in the sets that couldn't work without them. It might be different now, but for a while you couldn't get the 4 ports Power Control Hub outside of 2 or 3 sets. You could buy weaker and bulkier hubs separately, but the specific smaller new generation hub only came in sets. It's interesting listening to Lego designer interviews, when asked about future plans they'll often mention that some development is totally possible, they'll just have to wait for a set that makes use of it.