I’ll explain “due to legal issues”.
At first, Microsoft didn’t support cross-play on XBox One. They wanted video game money to go to XBox Division. But Microsoft can’t pay people to use Windows, so they need to do something to prop it up. Among those things is they decided to play up their “Windows Everywhere” strategy by enabling cross-play between games on Windows 10 devices and XBox One. Microsoft would love for Gems of War to support cross-play.
Nintendo doesn’t give a flip about cross-play. They don’t care if you buy an XBO or a PS4. They bet you’re going to buy a Switch because there is some game you like you can’t get any other way.
Sony hates cross-play. They fear it means you’ll play games on your $6000 gaming rig and then you won’t pay $800 for their PS4 VR Setup with Cheese or whatever. So part of the Sony licensing agreement is that your game can’t reasonably support cross-play unless you get an exception. (I think they’ve slightly relented on this recently, but I haven’t seen many effects.)
Fortnite, Minecraft, and other games that are supported are special. They are worth so much money that Sony had no choice. Sony tried to make Fortnite worse in retaliation and the end result was a visible drop in PS4 sales so they learned their lesson.
Even if Sony shifts (or has already shifted), I don’t expect a fast change for a couple of reasons:
- The console licensing agreements are lopsided, and can change on a whim. If the GoW team invests a lot in console cross-play, there is a big risk one or the other players will change their mind or make it cost extra money or some other burden.
- There is a lot of GoW complexity. What happens to guilds? What happens to Guild Wars standings? What happens to your accounts? Do you have to abandon one, or can you merge them? Most answers to these questions will make people very unhappy.