Layout for GUIs are hard. And HTML nor CSS weren't developed with layout in mind. The original idea was to mark up (the M in HTML) meaning and semantics and le

Layout for GUIs are hard. And HTML nor CSS weren't developed with layout in mind. The original idea was to mark up (the M in HTML) meaning and semantics and leave the rendering and display to the client entirely. If you consider that systems that were designed entirely around layout (Like QT layout https://doc.qt.io/qt-5/layout.html https://doc.qt.io/qt-5/layout.html), are complex and hard, you can imagine what happens when you try to do layout with a system that was never intended to handle this, must be backwards compatible, is a standard (not a lib or framework) and can be freely interpreted by renderers by definition.