A publisher would care about open data for several reasons:
1) Open data increases the value of all parts of the web by allowing programs, not just people, to utilize the data through interconnecting and joining it.
2) Publishers are evolving from linear supply chains focused on content delivery to users, to becoming marketplaces that optimize the number of interactions between users through networked open science.
3) The future of publishing involves networked open science where data is openly accessible, annotated with metadata, and linked together in research objects, increasing findability, accessibility, interoperability, and reusability of research outputs.