it stands to wonder why anyone writes or publishes books of collected poems at all In music there has been a transformation to creating "singles" and having an album be a "collection of songs" instead of a cohesive work of art.
The best bands, imo, are still releasing albums that are meant to be listened to all the way through. My guess is that books of poetry are similar. The best can be consumed poem by poem but collectively create something larger than the sum of their parts. You know, like Voltron. love that about art. The same can happen at a photography or painting exhibition too. So cool.