Unfortunately serviceability is not normally high in the initial product requirements, but I've seen a direct correlation between customer satisfaction in support and products/protocols/designs with good serviceability.
Some people just like ASCII, human readable protocols. There's nothing wrong with that, but it's a little silly to suggest that the options for a packed binary encoding in 2007 were limited because Thrift and Protocol Buffers were too new.
I'd be interested in the original designer's remarks on using existing wire serialisation formats.
I enjoyed reading through his thought process for designing a simple protocol which is:
* Easy to use (requiring little/no additional libraries)
* Easy to extend (simple keyword/value extensions)
* Immune to changes in technology
* (above all) easy to understandThat said, I think he didn't want a binary format in any case -- his "doing it again today" remarks point to JSON.
http://catb.org/~esr/writings/taoup/html/textualitychapter.html