Lack of incentives didn't stop the artists of the past. Many were able to secure patronage.
It is really, really difficult to build a career around patronage. A few people can do it. Most cannot.
The fundamental flaw of the "software should be free because duplication costs are zero" argument is that it ignores the total economic picture of software development. It's like saying "gasoline should be free because it costs next to nothing to run the pump motor at the gas station". Without someone's significant investment of time and money, that software (or that gasoline) is not going to exist. For software, the means of production is not a simple file copy, no matter how easy it is to invoke that COPY command.
We've been paying craftsmen for their work for many thousands of years. Software isn't any different if you take an honest view of the whole process.
What I've been observing, though, is people acting as if the software is free because copying is practically free. This happens all the time and nobody even thinks about it. Friends share programs, music, movies, pictures, documents and all kinds of data among themselves and they may not even realize the fact they're infringing copyright. I see my colleagues sending each other copyrighted scientific articles via messaging applications every week. Nobody really thinks about some journal's copyright, it's just "those people need this file and I have it, so I'll send it to them". Companies have been trying in vain to police this behavior for years. I don't think they're ever going to succeed. I think that's a sign this system is incompatible with current technology. What good is a law if you can't enforce it?
>It's like saying "gasoline should be free because it costs next to nothing to run the pump motor at the gas station".
I don't think this is the same thing. A more apt comparison to software would be "gasoline should be free because the pump is magical and can somehow duplicate existing gasoline, creating new matter in the process, and the cost is so infinitesimal we don't have coins worthless enough to pay for it unless we purchase a whole tanker's worth of fuel". I'm willing to bet that such a magical pump would drastically change how people perceive the value of gasoline. Even though creating that first volume of gasoline required a substantial amount of money, the magical pump can simply duplicate it endlessly.
In your patched-up analogy, someone has to pay for that first billion dollar gallon of gasoline. Someone did pay for the exploration, drilling, extraction, transportation, refining and marketing of the fuel; they paid for equipment, for people's salaries, for mineral rights, for the overhead of keeping a company running. It's a lot of money; it's an investment, and the investors expect a return. Take away the return and you'll find that none of the exploration, drilling, refining, etc. are going to happen. Have fun starving in the dark.
Software is no different, except that the "transportation" costs are close to zero. None of the other costs are zero, but the cheapness of that COPY command is all people really think about. They don't want to think about the engineers, the animators, voice actors, IT staff, management and rooms full of equipment necessary to create the product. They don't want to know about buying servers, spending money on marketing programs, creating sales pipelines, paying taxes and permits and making sure companies can hire and retain the folks necessary to make more product. I guess it's inconvenient to the rationalization.