Piracy is far closer to plagiarism, but even then only to a point. In plagiarism, one attempts to pass off the work of another as one's own. In piracy, one simply copies another's work for one's own use. They are fundamentally different.
This is why piracy is as prevalent as it is: it simply is not as bad as plagiarism, let alone theft. Most people have an intuitive understanding of this, and those who pirate do so without the cognitive dissonance that comes with acting against their moral code. It might be "wrong" in an abstract sense, sort of like lying on your resume is "wrong", but it's not wrong in the absolute sense of harming another person's body or property.
Declaring copies of data to be scarce is a convenient convention (for capitalists), because it allows data itself to be sold exactly like the scarce vessels (records, cassettes, books) which used to be sold as a stand-in for the data itself, and like other scarce things (bread, oil).
Without scarcity, capitalism cannot function. You cannot sell air (yet, but see "Spaceballs") because there is air all around so you can't run out of it. You can't sell "fours" because you can create as many fours as you need with a pen and paper or keyboard. However, the capitalists have successfully legislated that certain sequences of data are scarce. If this fictional scarcity of data collapses many people would be unable to make money selling non-scarce "virtual" things like ideas and data, and would have to fall back to selling real things. And they'd be unable to "allocate" these goods to people because everybody could just have whatever they wanted. Very good for people, very bad for capitalists.
Much like the attempt to legislate Pi (a half-true half-myth btw), this 'fiat scarcity' (just coined that) is doomed to ultimate failure. If not in the law, in practice. Like the War on Drugs.