You are right, you do not want to lookup documents that old, it is a waste of time... ... unless you are a German and the state asks for your time sheets three years in the past because you've gotten child support and are requested to prove your working hours. ... unless you happen to have an accident and your insurance is fighting with another insurance who's gonna pay and they ask you about the incident two years later ... unless you end up in a contract fight with the postal operator, that can take a year of mailing before being settled.

Some correspondences take years and only add a mailing every few months. You would like to have a thread-like view -- as in an electronic mail. That is the strength of document management systems.