A couple of thoughts here:

In my case I suffer from too much to do, so it's hard to keep ahead of everything. And also, I look at a lot of my projects as long term. I spend a great deal of time optimizing my sites for search engines, so it just takes more time to build traffic at my end. But I suspect a lot of webmasters are just overloaded and don't manage their time well.

Also, a lot of wm's are looking for a big hit, like $35 PPS, so they probably focus on those, not realizing that tons of other wm's are doing the same thing.

Finally, could be your content as well. You're in a pretty limited niche with armpits, they're simply not everyone's cup of tea.

I experienced a similar thing with Bearbound, I figure that site would sell like hot cakes, but then I figured out that even though they're bears, not a lot of traffic wants to see them tied up.

Michael