I don't race, and some of the people on here like umd could tell you so much more, even though you don't have to race to use cadence to get stronger. But, cadence can be used to train smarter riding. When you watch your cadence, you can see if you or slacking off. You can do little tricks like pick a cadence, and see how long you can hold it up a hill. Next time, see if you can go a bit farther up that hill at that cadence before you slow down. You will be amazed at how you can push yourself farther up that hill each time. If you learn to ride at a faster cadence than what might feel normal, you have the advantage of using that higher cadence when it fits a situation.

I truly wish some of the people that could explain this much better while ignoring the negative would weigh in.