I don't think there's anything that's fundamentally impossible (or even conceptually very hard) to solve, it's just that most of the times you're solving the interop problem with JNI/JNA. The opposite route is massively more complicated to implement and nobody wants to dump their time into that. IIRC, as a matter of fact, there are many amateurish level C->JVM compilers but nothing that you'd be comfortable working with on a daily basis.

I guess it boils down to "yeah but why".