Aren't JIT compilers technically pretty infeasible on iOS anyway because of security restrictions?
However, I speculate even the 2nd restriction is partly for business reasons because it prevents some third-party toolkits (such as those compiling to LLVM) from achieving high performance. You might remember that Adobe was compiling Flash to LLVM to allow devs to port their Flash apps to iOS, but since LLVM cannot do proper JIT compilation on iOS, it will reduce performance.
FWIW: WinRT imposes both the restrictions above. Android technically doesn't impose either for sideloaded apps. But if you want to distribute app through Google Play, the 1st restriction is indeed imposed.
I hadn't considered this before, but that means that you could potentially use JS as an intermediate representation for other languages in order to leverage Safari's JIT under iOS. Probably too inefficient to be worthwhile for any language that isn't a dialect of JS, but an intriguing concept nonetheless.
Javascript in Safari is jitted - but JS in a UIWebView used by a third-party app is not.