I agree that meta description and keyword tags are dead for the most part, especially for SEO purposes. But in some cases, the meta description tag is used to display content in the search results pages.

I have some pages that don't have a meta description and it looks like the search engines just pick a randon section of the page text to display on the search results page.

On pages where I have the meta description tag, that tag's contents show up instead.

Although the meta description tag probably doesn't help to get you ranked higher, it does give you the opportunity to present a more compelling reason for a searcher to click on your page.