This is because each desktop operating system using a different graphics rendering engine—Quartz on macOS and X/Wayland on Linux, for example. In order to write an application that works on all major operating systems, you either need to use a graphics library that has already done the heavy lifting of calling the native frameworks under the hood or you have to do it yourself. Or you can use a web-based graphics library that has also already done that heavy lifting, with the added advantage that you can use languages like HTML, CSS, and Javascript to easily create visual elements. This is attractive when the alternatives like Qt are notoriously difficult to deploy and force you to use C/C++.