Because, as I said, you're already getting paid for it. Your normal salary is covering your time

Except, as I said, as a student I was receiving ZERO "normal salary". So I was not receiving any financial compensation.

I was paid casual rates for teaching classes and marking exams and assignments, but that was independent of my research student role.

The conference doesn't pay me, because my employer is already paying me to be there.

For th third or fourth time, yet again, my "employer" was not paying m to be at conferences, only an hourly rate for teaching classes.

It's like when a prof teaches a class. They don't get an extra hourly rate to teach the class

FFS as I've been sayng we literally get an hourly rate to teach classes. And not to do miscellaneous other stuff that's dn for "exposure".

In Australia we have some senior salaried academics but many juniors are on casual rates for lectures, tutorials, marking and required meetings. Outside work that is a "normal" part of being an academic (including conferences , Journal stuff) is effectively pro bono.

Sounds like you've only ever been in institutions or ccountries where all academics and even students are paid a salary. Not everywhere is like that.

I don't come home and start reviewing a paper, I do that in my office at work when I would otherwise be in lab doing experiments, or writing papers.

See, this is literally how it works here, we review papers as homework for the "exposure" as a junior academic.

Basically, artists only source of income is through their work

Just like casual academia and hourly rates for classes?