285 million people are visually impaired in the world. Putting aside the SEO, meta-data and other discussions, I think this is a pretty meaningful argument in favor of doing it right.
You (and I to a certain extent) need to be more specific. You've provided a list of screen readers. What I was really trying to say was "when someone argues that a particular markup or technique has benefits, then they need to demonstrate a real user with a real need who will benefit using shipping technology".
So we would need to pick a particular point of contention and then we can argue the toss.
PS If you read the Mark Pilgrim IRC logs he caricatured the response he often found when criticising any aspect of accessibility best-practise as "OMG!!! YOU HATE BLIND PEOPLE!!!". It's an effective way of shutting down debate and doesn't help anyone.
Here are the user agents that make use of it:
- ChromeVox: https://chrome.google.com/webstore/detail/kgejglhpjiefppelpm...
- NVDA: http://www.nvda-project.org/
- Window-Eyes: http://www.gwmicro.com/window-eyes/
- VoiceOver: http://www.apple.com/accessibility/voiceover/
- JAWS: http://www.freedomscientific.com/products/fs/jaws-product-pa...
- Orca: http://live.gnome.org/Orca/
And two dozen others. And here a few living human beings that benefit from it:
http://www.youtube.com/watch?v=Mwoe7OjIxpw, http://www.youtube.com/watch?v=pntGp00HHr8, http://www.youtube.com/watch?v=dAw0SIkXm1o, http://www.youtube.com/watch?v=ZBzSXIEusoU, http://www.youtube.com/watch?v=-zSTJwIULYU, http://www.youtube.com/watch?v=6_TFHqIHBqM
285 million people are visually impaired in the world. Putting aside the SEO, meta-data and other discussions, I think this is a pretty meaningful argument in favor of doing it right.