As one who complained directly this being off-by-default to some python-dev folks, one small reason it's off-by-default in the bugfix releases is because it's l

As one who complained directly this being off-by-default to some python-dev folks, one small reason it's off-by-default in the bugfix releases is because it's likely to break people's tests if they use doctest. Pretty much everyone I've talked to sees this as an argument against doctest on at least some level. IIRC there were also larger concerns about poorly implemented systems that depended on hash() being stable for persistence reasons. I don't know the details of that, as I appreciate the nod to backwards compatibility and not breaking people on a bugfix release.