Look at it this way if I steal your trade secrets and clone your product after you spent R&D money on it I’ve essentially “stolen” both a part of your revenue and your investment.
Music, film and games cost money to develop and produce pirating them does incur a financial penalty and that does fall under the common definition of theft.
However as far as Apple goes if you buy a copy of their OS you can easily consider that acceptable since EULA restrictions on the usage can be ethically counter argued.