They don't. Java apps have been cross platform since their inception, .net is extremely close to being just as versatile, x11 is available on mac and pc, and py

They don't. Java apps have been cross platform since their inception, .net is extremely close to being just as versatile, x11 is available on mac and pc, and python will run on literally anything. There's a pile of cross-platform options out there for you. What electron does is reduce the barrier to designing UIs, since you can do it all in html and javascript and its just as easy as hiring the guys who did your website to design. Because the one thing all those platforms have in common? Aside from .net (which isn't mature), they all have absolutely hideous windowing systems. Just ugly.