I am about to insert an image where I use the filename as both the title and the description.
Now I will insert the same image again, after changing the label and the description on the Manage Assets page.
The first has the original alt attribute (the filename), whereas the second has the new alt attribute. Changing the label and/or description has no effect on the alt attribute of images already places on an entry or page.
Why do you care so much about the alt and title attributes?
Bob, in my case I have additional scripts running on some sites that extract the alt or title text to insert captions underneath the images.
If you want a consistent caption across articles--let's say you spelled somebody's name wrong and you want to update it across 3 articles--it would be nice to update the image/asset metadata once, and have that change be applied across all occurrences. However, that's not how it works--there is an association from image to asset, but not from asset to image.