By making this the default map in classrooms for centuries, with little context given to the reasons for its appearance, many people have necessarily had a truly twisted view of what the world looks like. There have been many different projections proposed and presented over these centuries, but none have really gained the same popularity as the Mercator one.
Given that the people who claim ownership and ensure distribution of this map have historically been white and rich representatives of the countries in the northern hemisphere, we may have a clue to the reason for its persistence. Why would any of these representatives and leaders have wanted their countries to suddenly appear smaller in favor of poorer countries?