The objective of this API is to enable smart card (PC/SC) applications to move to the Web platform. It gives them access to the PC/SC implementation (and card reader drivers) available in the host OS.
Smart cards are popular in the enterprise and governmental sectors. A governmental website could identify a citizen by communicating with a government-issued smart ID card inserted in a card reader without the need of external, native, applications. Similarly, an enterprise that issues smart cards to their employees could authenticate them in its corporate website using the employee’s card inserted in a smart card reader needing only the browser itself.
One might argue that there are better, more modern, ways than the low level, legacy, PC/SC, such as WebAuthn. But that won’t change the reality that PC/SC is widely used in some sectors of our society.
The explainer document has all the details.