Well, no, I didn't say "go pound sand" - I said Web MIDI is about enabling low-level access to MIDI devices, such that a Standard MIDI File player could be written on top of that API.
It would be nice to have Standard MIDI File playback in <audio>. However, the entire pipeline to play SMFs is not necessarily "free", and it's not yet clear that there's enough value to increase the required footprint of a web user agent to fulfill that particular need.
For context - Apple *REMOVED* the built-in player for SMF after QuickTime 7, and no longer installs a default General-MIDI compatible synthesizer IIRC. These are pieces that can be replaced, of course - but the first step is enabling the basic scenario (which Web MIDI does), and then proving a broader need in use cases.