Yes because it's a language of higher level than C++ that can theoretically run on all platforms. Now I don't know about you but I'd much rather write the core of my software in a language that can be used on all platforms. This way I can leverage the same business logic everywhere and just have different, dedicated logic for UIs.
I once tried to use C++ for this but the STL is supremely lacking in almost every way compared to the standard libraries that come with almost every other language. There just isn't much choice out there.
Gah, I'm not sure how you'd do that and still be able to deploy an application to the iOS app store. I would imagine cross compiling Swift would be orders of magnitude easier.
Java isn't married with a JIT, there are quite a few commercial AOT compilers.
Even Oracle is finally planning to add one after Java 9.