John Smedley was the president of Sony Online Entertainment, which later became Daybreak Games after splitting from Sony. In a recent (and now deleted) tweet he cited 'money' as the main reason for PlayStation not allowing crossplay between platforms: "When I was at Sony, the stated reason internally for this was money. They didn't like someone buying something on an Xbox and it being used on a Playstation".
btw when I was at Sony, the stated reason internally for this was money. 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.June 18, 2018
What's interesting about Smedley's comment is that would explain why cross platform play works between PlayStation and other, non-rival formats. Sony's has previously issued a response to Fortnite crossplay between PS4 and Switch, pointing out that crossplay's totally a thing. Just not with Xbox and Switch:
"We're always open to hearing what the PlayStation community is interested in to enhance their gaming experience. With more than 80 million monthly active users on PlayStation Network, we've built a huge community of gamers who can play together on Fortnite and all online titles. We also offer Fortnite cross-play support with PC, Mac, iOS, and Android devices, expanding the opportunity for Fortnite fans on PS4 to play with even more gamers on other platforms."
Combine Smedley's comment, "if we keep the pressure up this problem goes away" with Sony's "we're always open to hearing what the PlayStation community is interested in," and maybe there's a chance. 'Crossplay with Switch' is pretty much the point of interest right now for PS4 owners so maybe this isn't over just yet.