Pretty much every game is looking for post-sales DLC these days. Imagine all the GTA V DLC revenue a platform holder gets, and imagine they don't get that for GTA VI which everyone also plays on their mobile and buys content there.
DLC is easily restricted to the platform you purchase it on if the platform holder desires it. Again, using FFXIV as an example. Expansions for the game are basically just really large DLC packages.
- On PSN, you are required to buy them even if you already own it on PC.
- On PC it's more nuanced.
- The Steam version requires you to buy the base game and expansions as well.
- However, the stand alone FFXIV client (downloaded from Square-Enix or installed from physical media) only requires you to have a valid account and have paid for the content somewhere (PSN, Steam, physical copy from store or the Square-Enix website...it doesn't matter).
Of course, the platform holder can decide not to restrict it if it views it to be worth more to allow DLC purchased on another platform to work on their platform. IE - if they hope that the some of the people on another platform may get their platform and begin buying games on it.
IE - while you can attempt to lock players to your platform by locking DLC, you also prevent players that don't have your platform from migrating to your platform.
Currently microtransactions aren't limited like that. Again, using FFXIV, micro-transactions for the game are conducted on Square-Enix's website. Neither Sony nor Valve get a single cent from microtransactions in FFXIV.
That allows a F2P game like Fortnite to bypass the platform restrictions that Sony has for Game purchase and DLC purchase as micro-transactions are conducted in game. Although in the case of F2P games currency for microtransaction can sometimes be purchased on the platform (PSN, Steam, Xbox Live, iOS, etc.) as well as through the developer's own website. But they aren't required to do that on most platforms. PSN, Steam, and Xbox Live don't require cash currency for microtransactions to be purchased through their platform.
So, if we take a look at something like Fortnite, there's the opportunity for Sony to cash in on shared DLC or micro-transactions if someone starts playing it on a mobile device and gets hooked enough that they start to think about playing it on a dedicated device (console or PC). Since the DLC/MT is shared, there's no barrier to that player moving to PS4 as they won't have to rebuy their DLC/MT.
In that case, perhaps Sony never makes a single dime from that Fortnite player in Fortnite. But, they might make money from those players buying other games on PS4.
Regards,
SB