There's a few things about this

1. Many times you don't own the digital good, you subscribe to it. No I'm not joking, that's why services can usually take it away at any time. You normally own "a licence to play it on a single PC" or similar.
2. This isnt apples to oranges per se. Selling digital goods is fine, it's copying it. Similar to how photocopying a book and selling it would not be okay.
3. It's important to note there is a narrative push by companies too. They spend lots of money putting videos on every DVD saying "downloading is stealing" because if society thinks piracy and stealing is the same, it helps them litigate and make more money.
4. Your idea of a lost sale is a hard one, from a media company point of view, it's about making money. So if you can make people believe "a download is a lost sale" or "sharing a digital file is a lot sale" etc, then you can use that to sue individuals, isps, sharing sites, search engines etc and make more and more money while also having more power over your product.