The short answer? I don't have a good enough idea.
Living in San Francisco, in the current angel investment bubble, with a (tiny-but-nice) acquisition by Apple under my belt, and big plans to change the world, I sometimes feel like a freak of nature because I'm not hunting for funding. Why did I make that decision?
I spent the first year after I left Apple aiming to build a VC-backed company. I had a plausible story, built a complete prototype, deployed pilot installations, and sat in numerous boardrooms pitching partners. The trouble was, it was a terrible idea. I was following in the footsteps of Tacit, VisiblePath and multiple other enterprise email analysis failures. I had no comprehension of the torture of the enterprise sales cycle. The idea of analyzing email fundamentally creeped people out, no matter how strongly I protected privacy. In the classical model of how the process works, I would have got all this feedback from the VCs I pitched to. Aside from being pointed towards Tacit by one partner, I learned everything by painful trial-and-error. VCs loved the idea, they were deluged with email messages and made their livings through their personal connections.
The lesson I drew from that was that I was an idiot. I should be listening to customers and discount what I heard from investors. Get customer traction, revenue, and ideally a profit, and the opportunity would sell itself to potential funders. Obviously that also cut down the range of opportunities I could chase, but what I'd discovered in my unfunded year was that it's possible to build a lot with very little cash. By building fully-functioning prototypes, I could learn what users responded to, as well as what was technically possible.
The trouble is, after a couple of years of operating like this, I'm addicted. I've had many failures, along with a few partial successes, but I'm become so much better at understanding what people need, what's possible, and executing a solution. My failures are becoming faster and far more interesting. I may be living on Ramen noodles, but it's an amazing opportunity to learn. Just the process of fund-raising itself would take a massive amount of time away from that, and then explaining every month where their money's going, why I'm fishing with strawberries, and planning for the next round would take even more.
That's still a worthwhile use of time if the funding is going towards rocket boosters to strap onto a killer idea. I don't think it's lack of confidence that's telling me none of the approaches I'm working on has crossed the threshold where it's worth it though. There's funding available, I just don't think the strings attached make up for the help. Better to live frugally, consult when I have to, and focus on learning. The more progress I can make, the more I can learn before I need to buckle in to the rocket sled, the better. I'm looking forward to honing my ideas until I can build the real business I dream of, whether that's fully boot-strapped or with the help of investors.