Why is Debian not creating the 'wheel' group by default? It appears to be Unix tradition that a wheel group is created automatically, but Debian (and children, naturally) doesn't do so. Is there a rationale somewhere? Where else have you seen this tradition discarded?

Some unix systems allow only members of the `wheel` group to use `su`. Others allow anyone to use `su` if they know the password of the target user. There are even systems where being in the `wheel` group grants passwordless root access; Ubuntu does this, except that the group is called `sudo` (and doesn't have id 0).

I think `wheel` is mostly a BSD thing. Linux is a mix of BSD and System V, and the various distributions have different default policies with respect to granting root access. Debian happens not to implement a wheel group by default; if you want to enable it, uncomment the `auth required pam_wheel.so` line in `/etc/pam.d/su`.