[Animats]

CAD people got this a long time ago, but, unfortunately, HTML people never did. Layout is a 2D constraint problem, but HTML/CSS approaches it as a procedural problem, partly because early browsers were so compute and bandwidth constrained.

[SR2Z]

CAD is great at parametric design, which gets significantly more complicated when the viewport changes shape.

Taking a procedural approach instead of solving constraints is necessary for folks to stay sane when they're trying to get the same website to work on phones and desktops.