How does testing the website with actual users on their mobile devices provide valuable insights?

Testing with actual users on their mobile devices is crucial because it provides qualitative data. This means you gain insights into why users interact with your site in certain ways, their frustrations, and their overall experience, especially regarding how different screen sizes affect usability. While tools can measure loading speed (quantitative) and user behavior (quantitative), they often miss the nuanced "why" behind the data. User testing helps uncover pain points that automated tools might overlook, such as difficult navigation, unreadable text on smaller screens, or confusing layouts, which are critical for optimizing the mobile user experience. It doesn't eliminate the need for tools; rather, it complements them by adding a human perspective.