Nintendo and Microsoft have teamed up for a Minecraft commercial that seemed strangely historic for those of us who grew up thinking about console generations as a series of figurative wars. Both consoles were highlighted, both company’s logos were on the screen and the hook was the ability to play the same game across two consoles or using a gaming PC.

Sony was, of course, not involved with any of this. The company doesn’t support cross-platform play between consoles, and limits the use of Fortnite accounts on other platforms if they’ve ever been used on the PlayStation 4. In the case of Minecraft, Sony’s excuse from 2017 was that cross-platform support would make PlayStation 4 players less safe, a claim that Microsoft’s Phil Spencer rejected out of hand.

But it might be as simple as an economic issue.

“BTW when I was at Sony, the stated reason internally for this was money,” industry veteran John Smedley tweeted. “They didn’t like someone buying something on an Xbox and it being used on a Playstation. Simple as that. Dumb reason, but there it is.” Smedley used to be the president of Daybreak Game Company, which was once called Sony Online Entertainment. He’s now the general manager of Amazon Game Studios. The tweet has since been deleted.

This is the explanation that actually makes the most sense, and we can see the account issue come up in the FAQ section of today’s Minecraft blog post talking about the release of the “Better Together” update for Minecraft on the Nintendo Switch:

Q: What’s a Microsoft Account and why do I need it for a Nintendo Switch?

A: A Microsoft Account is a free account you can sign-in on device that allows Minecraft players on Switch to play with others on non-Nintendo devices like iOS, Android, Xbox One and Windows 10 via cross-play, Realms or Servers. Having a Microsoft Account also enables the portability of your MINECOINS and marketplace purchases to other devices and platforms. To create an account click here.

The game industry is turning into a business of accounts, not hardware, and you can guess how enthusiastic Sony must be about the idea of someone logging into a Microsoft account from the PlayStation 4.

But outside of the terminology, it’s the last part of the description that has to stick in Sony’s craw: The use of the Microsoft account is what allows someone to give Microsoft money for in-game items, and then bring those items onto other platforms. Sony only gets a cut of the revenue if these purchases are made on its platform, which is why this is a topic it’s willing to be so stubborn about.

And this is likely what Sony is afraid of in the grand scheme of things. Imagine a world where game accounts move from hardware to hardware willy nilly, and purchases made on one platform were accessible everywhere. Where’s the profit for the platform holders? If you buy all your content for a free-to-play game on another platform and use that content on the PlayStation 4, the hardware just becomes a conduit through which you play games you paid for on other platforms.

The play part of cross-platform play is the least important aspect of this issue for Sony. The important issue is the use of third-party accounts to purchase things away from Sony hardware, and then using them on Sony’s platform.

So why don’t Microsoft and Nintendo care? My guess is that Nintendo is Nintendo, a company that has already played by its own rules and has ridden that sense of adventure directly into huge profits, and Microsoft is currently way behind Sony in the console business, and this is a way to bring attention to something the Xbox can do that Sony refuses to match on the PlayStation 4.

But if Sony lets Minecraft purchases from Microsoft come onto the PlayStation 4, and it lets purchases from Epic Games come onto the PlayStation 4 through the accounts tied to other games and companies, it’s not going to be able to deny anyone else, which means that Sony would lost the ability to guarantee itself a heavy cut of all the virtual currency and in-game items being sold for those games.

That’s the nightmare Sony is worried about, and that’s why it’s been so unwilling to budge. The question is how much pain the company is willing to endure before it decides the lost profit is worth the positive press and player contentment.