[dazzawazza]

All of those professions do plenty of hours of "work" outside of "billable hours".

They all read professional publications in order to keep up with the progress their professions are making. In many cases this is a few hours a day of reading.

For most this is a chore but it's part of being a professional in those professions.

[huffmsa]

Reading papers isn't the same as doing the job though.

I read mostly technical content related to software dev / general tech, but I rarely create software outside of work.

[JohnFen]

I don't see the same sharp divide as you.

Studying, practicing, and improving your skills are just as much "doing the job" as actually writing code. It's all an essential part of production in the end.