It's the only job where you can make money without worrying about somebody else's opinion. Your only limit is you, not someone else's perception of you. There is absolutely no other profession in the world that permits this. I find that aspect alone maximally fascinating. There are other jobs where you can work remotely, set flexible hours, and there are businesses where you could conceivably make more money overall (e.g. start a very successful company like Facebook), but the idea that only you are responsible for everything and nobody else is awesome and unique, and is the ultimate reason I'm so attracted to it.