Many Python deployments involve large code based that are used in scenarios where processes are fork-and-exec'd.  When running in these environments code objects can end up occupying a lot of memory.  Because the code objects are on random pages and are ref counted the ref counts can cause all of the code to not be shared across processes.

If code objects supported the buffer protocol it would be possible to load code from a memory mapped file which is shared across all of the processes.