There are many documents that are archived on microfilm that hasn't been digitized. Libraries around the world store this microfilm so folks can look through them for the info they seek. For example, I've been digging into my ancestors who lived between 1850 and 1900. Many small towns had newspapers which covered the coming and goings of folks in town. Big players like newspapers.com make this info available under a subscription. The US Library of Congress also has a digitized collection. However, many other newspapers haven't been digitized.

Libraries are setup for you to browse these microfilms page by page. When you find something interesting, you can scan it to a thumb drive. However, it's tough and time consuming to find the interesting things up front. Ideally, we'd digitize the entire microfilm reel and then be able to browse or analyze it at home.