I never said that was the only consideration, I said it was the main consideration. Clearly you didn't read my first post in the thread where I said:
For people like me who getting so hard to get traffic from search engine, the leading niche directory is a place to go. Since i'm in software business, i pay for hotscripts and download.com, than i realize so many smaller script and software directory list my website even i didn't submit to their website. This is interesting. PR and other SEO things are the secondary benefit from submitting to directory. IMHO traffic is the first thing to be consider.