While Fortnite is one of the bigger games doing it, I don't think it's unique to Fortnite. Many games have seasons and constantly updating content. That's the bigger takeaway, not that Fortnite is successful with it.

Players will no longer stick around a year or more for new content. Back in the days when there was a dozen different games, maybe, but nowadays there's so much other content out there, why would someone play Overwatch for 4 years straight?