Handling more directories at once

Since I search some more directories through DigitalPoint, I notice that some owners in a single web directory actually owned at least three or more, or could be they're partners to it. I don't know why they need more than one web directory? Is it because they want more revenue sharing for it, or they just want themselves to become popular than ever. For me, as a webmaster, it's a difficult task like no other but money and time is involved here.

I noticed when I receive some notifications in my e-mail that my link has been submitted, they also include their other partner sites just to make things right for SEO strategies as well. I think it's a strategy like no other when it comes to SEO and promotion, they always do everything to prove everything.