Debugging text is easier and the bulk of the data is binary anyway, so there would be no great file savings with a "pure" binary protocol. That's the same ratio

Debugging text is easier and the bulk of the data is binary anyway, so there would be no great file savings with a "pure" binary protocol. That's the same rationale for HTML and text-based internet protocols -- they are easier to write and debug. This is a particular concern when you're talking about a file format that has to work on wide variety of architectures and operating systems. Having a common ASCII encoding makes it significantly easier to build an interoperable file format.