> There are some built-in iOS apps that can't be deleted at all, such as Photos.

Yes, because if you take photos you kinda need a way to view them. It would be extremely confusing if your pictures you took with Camera ended up being saved somewhere but you could not view them, so Apple seems to have just made it a requirement.

> But if a user deletes all the built-in apps that can be deleted, are they restored if the iOS device is reset? I would assume so, since wiping a phone is recommended before reselling it and a new user may be confused if default apps are missing, though I don't want to wipe my device just to confirm.

That's a good question, and I don't want to wipe my device either. I'll see if I can get access to a "burner" iPhone to test this.