My guess is that your startup just isn't that interesting, especially to general audiences like Lifehacker. Your tool is a tool for making tools, which is not what the average Mashable, RWW, or TechCrunch reader really cares about. They want a shiny new service to show to their friends on their iPhone or something, not a tool that will help their company make money. They don't even have companies, or websites to optimize.

That's your problem, I'd guess. The group of people you'd appeal is too small. (Of course, on HN, the demographic is quite different, and you got 28 upmods in 4 hours... in the middle of the night US time. This is probably where you should pitch -- not as many eyeballs, but more eyeballs that care.)