[danudey]

Other people have pointed out that the certificates don't last as long and you need to constantly re-sign your apps. This can be worked around, for sure, but it does mean that if you're out of the house when the cert expires, you cannot use that app until you get home.

It also requires a Mac; Windows or Linux owners of iPhones are out of luck.

Lastly, you lose access to a lot of features; push notifications, IAP, automatic updates, iCloud, etc.

Basically, if Epic wanted to do this, they'd have to let everyone download the code and assets for Fortnite (likely hundreds of GB), then users would have to build it on their devices (which probably would take hours), then install it on their devices, then they would have to pay via Epic and not through iTunes. Whenever they wanted to update Fortnite they'd have to update the source tree and assets and rebuild the app again.

And again, all of this would have to be on a Mac. I know a lot of people who own Macs which don't even have enough disk space to build something like Fortnite, even if they used it for literally nothing else.

TL;DR Epic would have to open-source Fortnite and users would have to jump through irritating and potentially impossible hoops basically every day.