> Why would I care if an app looks the same on Windows, macOS and Linux when I'm not using all those OSes at the same time ?
Sometimes you do switch, and having everything be the same in your editor is nice. I normally work in linux on a desktop and have a windows machine due to corporate policy. Because of COVID, I started working from home on my laptop and VNC'ed into my linux machine to do work. It worked fine until my ISP decided to be shit, so out of frustration I just switched to developing on windows. Since I was using IntelliJ, I just exported my settings from Linux, imported to windows and everything just worked and looked the same.
In theory, I kind of agree with you. But in practice, having a consistent experience across all OS'es is nice. The ship has sailed anyway, nothing looks consistent across different applications on the same platform anyway. Might as well have applications be consistent across different platforms instead.