Key Points
Customer
We are stuck with technology when what we really want is just stuff that works.
Fully responsive across any device
Fast time to first paint by caching and small footprint
Faster render by reducing number of HTML tags
Better accessibility by selectable font size and light / dark mode
Business
Good companies manage Engineering. Great companies manage Product.
Future proofed - HTML5 and CSS3 Standards compliant
Stay out of legal quagmire - meets WebAim accessibility requirements
Lower cost - no javascript means less code
Simplify maintenance - reduces complexity and repetition
Technology
It is not the strongest of the species that survive, nor the most intelligent, but the one most responsive to change
No breakpoints - uses design widths
Simplified customization with CSS variables
No dependencies and no bundler required
Supports complementary colour scheme