Yes they do. I've seen it a few times.Google generate description their own? Never see that before.
They are important because often Google will pick up something random for the meta description and it won't look good in the search results. So setting meta description manually insures that you have the right content, keywords etc in meta description - this will help increase CTR in the results primarily and also its just another indicator to Google on what your page is about - remember its best not leaving anything to chance in SEO.
Any idea why BHW (homepage) doesn't have any meta description? I always wondered but never got a chance to ask.