Because telling people capitalism began in the 16th century creates a confused and misinformed understanding of history that makes it more difficult for people to reason about the world.
I guess we'll just take your word for it then? Especially since there are comments in this thread already talking about how it started earlier than you say. You give no source and not even a compelling argument and we are just supposed believe you?
It wasn't like a "one day we weren't capitalist, and the next day we were" type thing, it was a gradual shift as I understand it, from mercantilism and feudalism.