This compain can be applied to paper too. PDF is not much more than precise document to be printed or exactly visually presented.
Why would I want document type that can't even refloat on display size to represent any longer written text that is supposed to be consumed on digital device?
And as a format, it's much more sane than, say, Word or Excel.
Even if the focus on "where do I put this glyph" means the original text isn't in there by default.
FWIW this is not a technical barrier; it would be absolutely trivial to associated blocks of non-flowed text with the layed out text.