Refusing to spec it would have just given us another two decades of Flash-equivalent hell. Developers want features, and you can either provide a road-map for making them cross-compatible and specified or you can refrain from doing so (at which point developers will do whatever, and then some private company will provide a closed-source solution, every browser will support it because it provides a service end-users want, and instead of any piece of the story being open the whole story will be closed and it'll be a quarter century before something standardized replaces it well enough to uproot the de-facto closed standard).