I actually finally made an account this year to leave a comment on this question[0]. I'm not familiar with what or why curricula are what they are so I can't really answer the question, but as a math teacher it'd be helpful for the OP to know that calculus and linear algebra are deeply related; the derivative of a function is the best linear map (i.e. matrix) that approximates it! For practical purposes, calculus is a toolbag to turn (intractable) nonlinear problems into (tractable) linear ones.

But apparently I can't comment as a new user so I guess the discussion will just be "because calculus classes use matrices in examples".

[0] https://matheducators.stackexchange.com/questions/26417/why-...