Micropayments use case
I was listening to a recent episode of Ben Thompson's Sharp Tech where he was discussing Twitter's plan to launch some version of micropayments. Ben reiterated his position that he thinks micropayments are unlikely to work, since they go against the interests of the publisher.
His argument essentially says that what subscribers sign up for is the on-going production of content, rather than single pieces of content at once. This results in a more stable and sustainable stream of income for the publisher, who doesn't need to keep producing "hit" content that will make a big enough splash to attract lots of micropayments. Instead, they can focus on providing consistent content over time that appeals to their core subscriber base.
I agree with this take as it applies to niche sites, like Ben's Stratechery. It absolutely wouldn't make sense for him to carve up his content and sell it piece by piece, the risk of cannibalization from his large membership base isn't worth it. However, not all publishers are niche sites.
I think a better use case for micropayments might lie with local and regional news publications that have a limited reach in terms of geography. But they might have certain content that has broad appeal, for example, content that might appeal to tourists who are visiting an area or when global news events intertwine somehow with a certain area.
In these cases, you could have local publishers who have a fairly small membership base that lives in that geography and has a vested interest in supporting the on-going production of new content. While micropayments could be a way to reach people who would never have an interest in subscribing full-time, but want to access the limited amount of content that has some type of cross-over appeal.