For me it's the efficiency. The 90's era Windows UI and applications ran productively on machines with 8MB of RAM. That's an enormous amount of value for what

For me it's the efficiency. The 90's era Windows UI and applications ran productively on machines with 8MB of RAM. That's an enormous amount of value for what amounts half today's desktop CPU cache. The limited memory forced developers to conform to the OS provided API and resources (fonts, color pallets, image formats, etc.) and the result was small, fast, consistent applications. Today this discipline survives in mobile devices. Meanwhile, our desktop operating systems are festooned with a multitude of widget toolkits and language runtimes yielding wildly diverse, inconsistent and often fragile behavior and require 3+ orders of magnitude more memory. Aside from (usually) pretty nice font rendering, what has actually been achieved with all of this?