A couple of reasons. It's the ideal cadence for burning fat (now I have your attention!) Pushing heavier gears taxes your muscles more than your cardiovascular system. You end up burning more sugar, generating lactic acid, and getting more fatigued over time. Watch the pro's. Lance rode at 100 rpm for the whole Tour de France. Your body needs a mix of fat and sugar to ride (a LOT more on that, later.) It's like a carburetor that mixes air and gas. Heavier cadence - less fat, more sugar. Lighter cadence - more fat, less sugar. And we all want to burn fat.
So this morning, back on my bike after two weeks, and riding with Guy Sapirstein for our "regular" 18 mile ride, I was thinking about cadence. It turns out my cadence is in the 70's - not bad, but not there yet.
I also realized that thinking about cadence, in the terms Hue suggests, is also relevant for venture capital. Startups need to match their activity (and their spending) to the conditions around them. In order to build and maintain momentum the trick is use the right mix of human, intellectual and financial capital (don't ask what is sugar and what is fat). Too slow and the energy level goes down, money is spent with no results and the venture fails. Too fast and the people feel burnt out, the money is spent down before the benefits of building can create the momentum to get the next financing, and again the venture fails.
At the right cadence, we spend enough to grow momentum but without getting ahead of ourselves. The company learns how to grow just ahead of the planned growth path so that each extra dollar spent yields more than a dollar of new value to the venture. Success!