Performance is one of the most important things that you should take care of in your app. Your users need to use your app smoothly with no interruption or hanging. They have something to do, and they have to do it fast. When you develop your application, you develop it for a platform, not for a specific device. For example, you develop an iOS application, which will run on different types of devices with different CPU capabilities. That's why, measuring your app performance is very important, so you can find the areas that need optimization.