How do people manage to manage hundreds or even thousands of open tabs? And most importantly, why? Are they using tabs instead of bookmarks?

Usually I have no more than ten. Even when searching/researching something it doesn't get more than twenty - open all the interesting search results on the first search page, usually that's enough to find whatever I'm looking for. If not, tabs are being closed one by one or are being bookmarked with appropriate tags. Repeat for the next page of search results.