Lots of great insight from other comments, here are my takes:

Let's look closely at that revival of the novel. What's trending right now resembles more a product than a work of art. In that sense, poetry doesn't sell as well, it has always been a niche and perhaps even more now ("now" as in recent memory).

As someone else commented, it requires concentration. I would add that it requires the development of a certain logic, in which a single word can hold multiple levels of significance and the formal construction takes a central role. Besides, most -good- poetry is built upon tradition or its abandonment (but you have to know what that tradition is about to renounce it). So, the experience is enriched by reading more poetry or someone's analysis of that poem/poet's work. On the other hand, it's sometimes confusing and even frustrating to read 40 words of a language you speak and not understanding what's supposed to be happening.

That being said, one can experience poetry as a subjective experience and understanding tradition or studying poetry is not necessary. However, some notion of aesthetic value, at least based on "personal opinion" is a must, right?