It's first and foremost a methodology that plays into your design infrastructure. Whatever tooling floats your boat is absolutely fine, but the difficulty comes when you have to scale your design decisions across SVG, Sass, Tailwind, React Native iOS, Android, Figma, various prototyping tools, and for several company brands, dark mode, high contrast mode, etc.
At a certain scale, design and brand teams need infrastructure to drive change. These teams rarely have sufficient engineering headcount (if any) to build such tooling and delivery pipelines all the way to the user. Having interoperable formats brings alignment across design and engineering toolchains. The industry needs this methodology to be baked in, rather than requiring folks to build their own tooling.
At a certain scale, design and brand teams need infrastructure to drive change. These teams rarely have sufficient engineering headcount (if any) to build such tooling and delivery pipelines all the way to the user. Having interoperable formats brings alignment across design and engineering toolchains. The industry needs this methodology to be baked in, rather than requiring folks to build their own tooling.