We're talking about the crime of theft and the civil offense of copyright infringement. There is no argument about word meanings or technicalities, just what the law actually says.

Media companies want copyright infringement to be considered theft, and they've lobbied the government to try and change the definition in their favour, but the fact is the law distinguishes between them. Copyright infringement is wrong, but it is not a crime and nor is it theft.

If you're selling apples, and I steal and eat an apple, that's theft. You no longer have an apple, you had a cost price for that apple and you can't sell it anymore to make the profit you would have made. Meanwhile, if you sell a game and I copy that game, you still have your original copies. Yes, you haven't had the money I might have paid for a copy, but it hasn't cost you anything and you still have an infinite number of copies to sell. If I was never going to buy the game from you anyway, then you wouldn't have even got that either way.

The US is weird though, in that the courts award statutory damages for copyright infringement. If you fileshare a few songs to a pool of users they might stack up the fines for each user you shared to up to hundreds of thousands of dollars - nevermind that they never would have made that money from selling to all of those people you shared it with. In the rest of the world, they deal with actual damages, and claims for copyright infringement were rarely if ever very large.