Because you might be exporting it to an un-friendly country.
Don't try to apply logic here -- "But can't they just compile openssl or just use Linux!? or some library..." -- this is government contracting and security world, regular logic doesn't work here.
For exporting to friendly countries via App Store, you'll need an ERN. I'm not sure if the App Store will accept submission from unfriendly countries. It depends which one I guess.
Apple itself probably doesn't really care. Just needs to cover its ass in case Uncle Sam looks and asks questions. They can now say "We have enabled these checks and features on our side".
