Well, I would say the common argument is that you send an intermediate format to decouple yourself from the specifics of the receiver. HTML is an intermediate f

Well, I would say the common argument is that you send an intermediate format to decouple yourself from the specifics of the receiver. HTML is an intermediate format and the client is free to render it how it sees fit for the device on which it is running, which allows compatibility with newer and different clients. It's like shipping some intermediate bytecode doesn't seem to make sense, because every client needs to compile it, until you realize it allows you to ship one format that can even be used by many different architectures and even new architectures that didn't exist when you emitted the bytecode. At the cost of a second component that needs to be present on the machine to do the compiling. When a vast majority of clients is the same or sufficiently similar, it may of course make sense to offer an optimized format, that requires less client-side processing But what would such an optimized format for the web be?