Since when is TTS a feature that can be "disabled" on a per-book basis? It's a software feature, not a content feature. Even if it's an artificial restriction supported by e-book readers, what's stopping anyone from copying and pasting the text into a general-purpose TTS program to read it for them?
What was said was that the publishing companies lobbied for ebook readers to not include the feature. And you have to admit, it would be far more convenient for someone visually impaired to have TTS actually in their ebook reader itself, so they can use it without needing to be home or to be carting around a laptop.