because there are so many directory submit to dmoz every day & before approval it is manually viewed by dmoz so it takes time to get listed.
Actually, i've submitted to DMOZ once a time and got listed into DMOZ in 2 weeks. So it is not so clear as you wrote above.
Two things you need to ensure before submitting to Dmoz 1. Content - Do you have something really in ur site? 2. Most Appropriate Category - You need to choose the most appropriate one among categories that are very much related.