Apple is at least providing some tools to help with this - for instance, you can specify a storyboard whose initial view controller will then be used as the app’s launch screen; this avoids the problem of separate launch images for all screen sizes, resolutions and orientations their app supported.

http://oleb.net/blog/2014/08/replacing-launch-images-with-st...

I seem to recall Marco Arment took a bit of pride in having 100% procedurally generated graphics with overcast, so that he didn't have to create/ship any bitmapped images whatsoever.