Everyone's an armchair economist so I wouldn't count econ out.

I think that math/physics are more accessible to the layman. I know where to go if I want to get deeper into this subject.

I really don't know how to start becoming an amateur chemist or biologist. I've wanted to learn more about synthetic biology and gene therapy, but it's not as simple as cracking open a math book or going to a dev bootcamp. I wish these resources existed though! My best guess is because exploring chem and bio have bigger resource requirements like lab space.