Why on Earth would MS set it up that way ? ?
Sometimes they manage to befuddle me...
it might be related to the fact that a /r scan of a drive can often take at least 45 minutes to an hour on the average drive. They sort of figured that people would want to use their computers, not watch it scan it's drives!
hairsplitting: the /r, according to the /? help, stands for "recover" (well, it says "scans for and attempts recovery of bad sectors") I'd go with "repair" at least in some sense, but at teh same time /f stands for fix and fixes most other errors relating to everything <but> bad sectors.
Also, chkdsk /f will clear the dirty bit, and won't take a spinsters weekend to complete. by default a boot time autochk is passed the /f switch.
Lastly, you can query the dirty bit of a drive using fsutil:
fsutil dirty query C:
you can set it, as well. but not unset- only chkdsk can turn off the dirty bit. (well, and of course disk editors and other utilities)