You're completely correct but unfortunately, this doesn't matter in practice. It's true that thanks to formats like PDF/UA, PDFs can have decent support for accessibility features. Problem is, no one uses them. Even the barest minimum for accessibility provided by older formats like PDF/A, PDF/A-1a are rarely used. Heck, just something basic like correct meta-data is already asking for too much.
This means getting text out of PDFs requires rather sophisticated computational geometry and machine learning algorithms and is an active area of research. And yet, even after all that, it will always be the case that a fair few words end up mangled because trying to infer words, word order, sentences and paragraphs from glyph locations and size is currently not feasible in general.
Even if better authoring tools were to be released, it would still take a long time for these tools to percolate and then for the bulk of encountered material to have good accessibility.
This means getting text out of PDFs requires rather sophisticated computational geometry and machine learning algorithms and is an active area of research. And yet, even after all that, it will always be the case that a fair few words end up mangled because trying to infer words, word order, sentences and paragraphs from glyph locations and size is currently not feasible in general.
Even if better authoring tools were to be released, it would still take a long time for these tools to percolate and then for the bulk of encountered material to have good accessibility.
This recent hn post is relevant: https://umij.wordpress.com/2016/08/11/the-sad-state-of-pdf-a...