But what exactly is it with these random master curricula?
Libraries have required masters in library science for decades.
Running a library is a significant management and administrative undertaking. In the same way you'd expect a museum curator to have at least a master's in the subject of that museum (whether history, art, natural history), you'd want the person who actively manages a library's catalog to have significant education/knowledge about which books to buy, which periodicals and electronic services to subscribe to, which titles to get rid of, operative lending agreements with other libraries, the budget and personnel issues that come with operating a library, the grant applications and other funding requests that come with running the budget, etc. Then, there's a benefit in further specialization in the database tech, archival practices, supporting education/research for specific institutions with need for in-house libraries (schools, universities, law firms, labs, etc.)
The ALA has long recommended that librarians have MLS/MLIS, and the librarians I've worked with definitely had useful specialized knowledge at helping me navigate sources and subscriptions for identifying good materials and accessing those materials. It should be a highly educated field with highly educated workers.