Because a tradeoff of relying on calculators means the average person can't do simple math on their own. It would be bad for society if a crutch for general thinking dulls those skills the same way calculators dulled home economics skills. In theory people could pull out a calculator at the grocery store but I've never seen it happen.
I don't know what you mean by "home economics", but to me, that encompasses things like balancing a checkbook and making a budget and taxes and understanding how savings and debt and compound interest works how to choose when to save and when to go into debt. The sort of money matters that apply to any schmuck trying to live in the world. The reason so many people lack those skills is that for the most part we don't teach them in high school. Calculators have nothing to do with it.
Thank god we still teach quadratic equations, complex numbers, hyperbolic trig functions, and geometric constructions though. I don't know what would become of the world if most people didn't understand those things when we set them loose in the world.