I’m old and we were poor: my family got our first microwave oven about the same time as I started to learn calculus in 12th grade.

Both changed everything in an epistemologically qualitative manner. Life before calculus/microwave, and life after calculus/microwave.

How did we warm up leftovers before the microwave?

What did the world look like before I learned calculus?

Once you get obsessed with something, you'll see it everywhere. For you, that's calculus.

And no I'm not kidding, a couple years ago when I was studying distributed systems, I saw the CAP theorem everywhere. Why isn't distributed systems part of the high school curriculum? It's used in basically ALL computing devices (before cloud computing, distributed system theories were applied in multicore systems...)