> Genuinely interested in knowing this - if you can compile ruby , why cant you compile a program?

I would think that the fact that Ruby constructs that look like what would be compiler directives in a more static language (e.g., Ruby's “require” vs C’s “#include”) have their semantics defined in a way which both depends on and affects runtime state means that AOT compiling Ruby in the strict sense gets you very little, whereas running it to a certain point AOT and saving the runtime state gets you closer to what you'd expect from compiling based on usually-compiled languages.