1. The Web Content Accessibility Guidelines are a Web Standard.
2. If you want to make websites you need to follow them as much as you follow other Standards like HTML or CSS.
3. They are an integral part of the Web.
1. It can guide you (as Design Principles) to an accessible, usable user experience and tells you what the minimum requirements are.
2. It can tell you when you have failed to provide accessibility.
When you provide captions, you want to provide good captions.
When you provide alt text, you want to provide useful alt text.
When you have a visible focus style, you want to make it extra visible.
It is also the most efficient way to ensure accessibility. To look at WCAG and then use it as the North Star, always checking if you’re on track.