why should we use local variables while we have a complete design system already?

Hello there,

I am using Figma Professional plan for almost 3 years and built a strong design system to use across projects. Now, one of my colleagues raised this subject to define design local variables.

I read about the local variables and still don’t get the point of it while we use a rich design system and changing a component and or a property, it changes across all projects, why we should use local ones?