I dont understand what's the problem they are fixing. Why would someone go to a 3rd party site for firmware files when the vendors have download sites? Or is this really about the vendors agreeing to provide linux compatible CAB files?
This is mostly about the server manufacturers, and their commitment to supporting their Linux server customers (which may include some larger data centers), who are in various stages of insisting on fwupd/lvfs for firmware deployment rather than unique (and often Windows based) executable files for updates. Helping to pay for the bill to maintain the lvfs repository allows those manufacturers to compete for the large sales to customers who now have a fwupd/lvfs requirement in the RFP.
While some vendors are starting to include their professional workstations/desktops/laptops with fwupd/lvfs support, most still just provide a Windows executable for the consumer space (because the vast majority of consumers run Windows, as it is not, and never will be, the year of the Linux desktop).