Why Negotiation is difficult in the Creative Space?

Assume me being a self taught video editor, in the second year of college. I am studying a normal degree, which would land me up in a base level 9 to 5 Corporate Job.

Out of nowhere, a Company comes and asks me, if I would like to work for them, as an Editing Intern. Now, high chances that they convince me to work for free, saying that in return I'm getting the exposure and work experience as an editor to add to my Portfolio. Cool.

Now, let's say, if money conversation happens, then too, they'd pay me way way way lower than what the Market Rates are. And I too would happily accept it. Let me tell you how my brain would work in a situation like this.

"I was any which was learning editing just for fun. My expenses are borne by my parents. Now this company is atleast giving me some money to do something that I already enjoy doing. Atleast X>0. Thus, I'd be like cool, XYZ company, you have my time. Go ahead, exploit me."

How to negotiate in such situations? You know that if you demand more money, they'd just slash you off, and take another guy. You fear losing that X amount that you are offered, and eventually you end up losing your time.

@Papaocus @VedantRusty
Do go through this thread.