Exporting to .so (a) makes it non-portable (you suddenly need to ship a whole compatibility matrix of .so files including a Windows DLL or several) and (b) severely constrains the language design. It's very hard to do this without either forcing the developer to do explicit heap management using the caller's heap or very carefully hiding your VM inside the shared object .. which has interesting implications once you have multiple such libraries. Also you don't have a predefined entry point (there's no equivalent of DllMain) so your caller is forced to manage that and any multithreading implications.

It basically forces your language to be very similar to C.