Sony screwed up with Fortnite. When Epic Games' blockbuster landed on the Nintendo Switch in June, it included cross-console capabilities for every platform except PlayStation 4, due to Sony's long-standing reluctance to make nice with rival hardware manufacturers. Sony fans were able to play with people on PC, Mac and mobile devices, but they were locked out of games with Xbox One or Switch buddies. This all meant PS4 players with existing Fortnite accounts couldn't access them on Switch, and vice versa, so plenty of folks ended up creating a separate profile for each device.
Source: Epic Games