"Most people don't need to know why 2 + 2 = 4, they just need to know that it's true."
While most people don't need a rigorous proof that would take Russell and Whitehead hundreds of dense pages to reach that point, even a small child has to have enough of an intuitive understanding of how addition works for 2 + 2 = 4 to be meaningful to them. That's why we do exercises with pennies and talk about "if you have 2 cookies and I give you two more cookies" to drive the point home.
"Really, if indoctrinating them would be the point of cursive writing there'd be much more effective ways to do it."
You argue as if cursive writing is the sole means by which schools teach children to accept arbitrary, irrational authority. I don't think it's a "conspiracy" per se, just part of how the system works: when the system is characterized by regimentation and submission to arbitrary authority, it's a lot easier for useless things like cursive to be taught.