It is because History/history is just a representation for a country of itself.
It is a myth, a construction of identity.

E.g.: English, you didn’t win Waterloo. A coalition under the command of an English general did. Trafalgar didn’t prevent England to speak French because the Grande Armée was yet marching to Austerlitz… And Nelson destroyed “only” half the Franco-Spanish fleet… Advantage which was lost immediately after because the storm…

French: Joan of Arc was not a maid from Lorraine, and didn’t lead armies to victories… She was most probably the natural daughter of the Duc of Lorraine and was invented by the future King of France PR. La Hire and Gilles de Rais were in charge of the armies…

And we can find a lot of example like these…

It is less a lack of knowledge than a self-centre attitude, encouraged how our history is taught.
Who really realise when we study Egypt that it is in fact African’s history? Who just realise than when we speak of Alexander the Great, the Chinese had a full history of great kingdom builders?