While that's true for cPickle, it is not for pickle. The pickle protocol
itself is defined in terms of the "raw-unicode-escape" codec (see
pickle.py).
Besides, you cannot assume that the Python interpreter itself is the
only use-case for these codecs. The "raw-unicode-escape" codec is well
usable for other purposes where you need a compact way of encoding
Unicode, especially if you're strings are mostly Latin-1 and only
include non-UCS2 code points every now and then. That's also the reason
why pickle uses it.