The truth of the matter is that this decision benefits no one. It hurts players who just want to party up with friends, it hurts developers who want to utilize cross-play that now have to deal with issues like the recent Fortnite account lockouts from the Switch launch, and it hurts Sony by making the PS4 a less appealing choice for gamers that are considering their options for multiplatform games.
Source: N4G PC Sony's Stubborn Stance on Cross-Play Is Embarrassing – IGN