netcfg still has various bits of code to support checking whether an
interface is listed in /var/run/stab.  As far as I know, that was only
created by pcmcia-cs, which we stopped using in 2007 and which has long
since been removed.  hw-detect's changelog mentions this:

hw-detect (1.54) unstable; urgency=low

  [ Joey Hess ]
  * Remove cruft left over from the days of pcmcia-cs.
    - pcmciautils doesn't create a cardmgr.pid, so stop looking for it to
      determine if pcmcia is started. Look for the pcmcia_core module being
      loaded  instead.
    - No need for funky redirections when running the init script as it no
      longer starts a daemon.
    - /var/run/stab was only produced by pcmcia-cs, so the whole
      gen_pcmcia_devnames section can no longer run; remove.
    - Only modify config.opts in /target if pcmcia_resources is preseeded.
  [...]