You can write a library/tool that does exactly that, and the JVM offers an API precisely for that purpose. The reason such a tool isn't offered out of the box is that it trades off performance. For example, the JIT can optimise a variable or even an entire object away. When you want to inspect them at runtime, this would trigger a "deoptimization", where the representation would go back to the original bytecode from the optimised machine code. Observability that doesn't trigger deoptimization is, therefore, encouraged, but everything is available.
