Snippets we show tend to focus on full-sentences or enough context to describe what a page is about or relevant to a search. If we have a match that's strongest simply because a quoted term appears in ALT text or some obscure menu item, that probably doesn't generate a compelling snippet in how we normally would measure things. But given that for someone doing that quoting, seeing the quoted area might be the most important thing. So the regularly snippet process isn't as helpful -- and it's something we'll look at.