The first around the world sailing record for circumnavigation of the world was Juan and the remaining members of Ferdinand Magellan's crew who completed their journey in 1522. The first solo record was set by Joshua Slocum in the Spray (1898).
Most races or solo attempts start from Europe. Due to the configuration of the continents, sailing around the world consists in sailing on the Southern Ocean around the Antarctica continent, passing south of Cape Horn, Cape of Good Hope and Cape . Since 1918 the Panama Canal is an option but the locks must be entered and exited using engine power. Large stretches of the canal can be crossed under sail power.
Yes, people need to know how long it takes to sail around the world. Without this information, people who would wish to circle the globe by boat would not know how to prepare for their journeys. Were they to know how long this takes, they would be able to pack enough food and water.
As Maslow posited there are a hierarchy of needs for humans. Knowing trivia is nice, but not necessasry. Generally, what humans need is food, shelter, clothing and the like. General knowledge is another thing that people need. Trivia is not important and in a world where children are being slaughtered in Syria, trivia probably is not high on the list of elective things.
No, people do not need to know how fast you can sail around the world. The fact that you can sail around the world in less than 50 days is an interesting fact as one would assume that it would take longer to sail around the entire earth. Thus, it is good to see this information one time.