According to this definition, dumpster diving would be theft. The harms caused by theft and copyright infringement are different. Calling them both theft is just a marketing ploy. Stealing something deprives the owner of its use. Copyright is a monopoly granted by the government to an artist on a piece of intellectual property. This is socially beneficial because it means more people can make a living by creating art. Copyright infringement means evading this monopoly, and is harmful for the same reason that granting the monopoly is beneficial.
For example, dumpster diving is neither theft nor copyright infringement. It's not theft because taking food that has been thrown away isn't depriving anyone of its use. It's not copyright infringement, because we as a society do not deem it socially beneficial to grant anybody a monopoly on food production. This is true even though the dumpster diver is taking food without paying the farmers who produced it.
In many jurisdictions, it legally is. Morally, I agree that's bullshit.
But taking something without paying for it is not always theft; and one could imagine thieves paying a token amount for something in order to claim it is not theft.
Most importantly, copyright infringement, unlicensed use, and piracy usually fall into the category of "IP theft," which differs from real theft of physical property in important ways such as the harm caused to the owner (e.g. potential lost sales or licensing revenue vs. losing a physical item) as well as associated penalties and remedies.
> In the case of games, music, etc, you don’t pay for the file itself but for the work the artist put into it.
You're paying for the file and the rights to use it.
A lot of countries already have this. There's an additional tax on media storage devices such as CDs, HDDs etc. The money is then given to some copyright association that supposedly hands some of it out to the content creators.
You aren't paying for the work the artist put in, if you were that would be called a commission. You are paying for the right to experience a copy of the artist’s work. Usually you’re not even paying the artist, either. The studios and publishing companies reap the profits. It’s not different for studio developed games.
Do I pirate things these days? No, I am capable of paying and we’ve figured out streaming. Will I buy a proprietary product without trying it first? Probably not. Would I pay if I didn't have the means? Absolutely not.
I firmly believe that once a work of art has been created, it is oppressive to try and dictate who can experience it. I’m copyleft, not a rampant pirate.