I agree. If one matters to the SE, the other should as well. However, I've tested and tested, and none of my title attributes have ever been indexed. Alt text for a linked image does get indexed. Hopefully, Google will change this at some point, because I really believe that one is as useful as the other, and neither is more prone to abuse than the other.
If you mouseover an image that is a link it will display the alt text.
If you mouseover text that is a link it will display the title text.
I fail to see the fundamental difference that would make one a valuable inclusion for search engines and the other not.
In fact, IE seems to treat the title attribute as more important than the alt: if you mouse over an image with both alt and title, I believe it's the title that will display in the popup. You could say that it's only under those circumstances that IE becomes compliant in that sense, allowing the alt attribute to only display when the image does not.