A user might be operating in front of a mobile screen and a desktop screen, but their expectation changes widely on both devices. A user in front of a mobile device is a little less patient, as they are mostly “on the go” compared to when they are in front of a desktop. Mobile devices have changed the overall user experience and how a user perceives a website nowadays. In short, we need our content to render dynamically on mobile and desktop screens abiding by their requirements. If we could do that, we could create a responsive design with content specific to the device users.
For example, you cannot hide a “Login” button on a dropdown or hamburger menu in the corner. While you can do that on a desktop screen (even though it’s a bad design!) and the user will find it. The developers cannot mess up with the mobile design, considering the traffic size and data generation a mobile device is responsible for. Also, we have a lot to share with our users on the developer’s end and want a large screen space to accommodate everything.