Nowadays we also need mobile browsers which don't exist on desktop machines. Several years ago, in a 'desktop era' it was enough to install all the web-browsers on the developer's machine and review a website in them. Besides the adapted for mobile devices user interface, we also should ensure it works perfectly on a great variety of devices, screens, operation systems and web-browser engines. This brings new challenges for web designers and engineers.
Mobile first! It became true in the end of 2016 when a mobile web-browsing eventually overtook a desktop one. Victor Grinchik How to Install iOS Simulator and Android Emulator on Mac for testing and debugging your websites and webapps Introduction
