There have been prior attempts at getting rid of the GIL, but it was found that the addition of all the extra locks to ensure thread-safety actually slowed down an application by a factor of more then two. In other words, you would have been able to get more work done with a single CPU than you would have with just over two CPUs. There are, however, libraries such as NumPy that can do everything they need to without having to interact with the GIL, and working purely outside of the GIL is something I'm going to be exploring in greater depth in the future chapters of this book.
It must also be noted that there are other implementations of Python, such as Jython and IronPython, that don't feature any form of Global Interpreter Lock, and as such can fully exploit multiprocessor systems. Jython and IronPython both run on different virtual machines, so, they can take advantage of their respective runtime environments.