Well that not bad. That works out to 0.00847457627118644% of the over 590,0000 categories in your instance of not being updated in a year.
There will always be categories that rarely get touched. Some of the reasons are it's not much fun wading through 100's or 1000's of submissions to find the few sites that belong in spam ridden areas. That's why many editors may add a site they find, but not one in the "q". Some dialup users can't even edit in those areas because they will time-out from the 1000's of submissions in the "q".
I think in the past 9 months dmoz has added many more sites to their index than Google has ;)