Imagine this scenario: You own and operate a successful bakery within your small neighborhood. Your customers flock to your store for your fresh-baked cheese rolls, the delicious cupcakes you bake daily, and especially for your personalized service. You know most of your customers by their first names and can rattle off their regular orders from memory. You've got all the customers you can handle and more.
Then, one day, another bakery opens a mile away. Your business is still going great 6 months after they open. Gradually, however, you notice fewer and fewer of your regular customers coming through the doors. You're seeing some new customers but they don't seem to be buying as much as your regulars used to.