I guess IIS and Windows Server have an important role providing high performance HTTP service hosting nodes in Azure. If this effort from the .NET team can revive the future of .NET server-side development, the server team can capitalize on the integration of the managed stack on top of the kernel-mode http.sys web tier, to provide a first class hosting environment for ASP.NET applications on the Azure cloud. Microsoft is the one hosting provider in the world who can scale out Windows servers without having to worry about license costs.
Amazon and Google don't have to license their cloud technology, so why would Microsoft (be forced to adjust license costs. or to license it at all)? (Unless MS were to become the dominant hosting provider and some anti-monopoly law or regulation were to come into play, but right now they are far from there.) Licensing IIS is a side business to the cloud hosting business.