You'll see that that's far from including all root or intermediate CAs that are active on the web.
But the major browsers have incorporated the Forum's standards directly or indirectly into their root certificate programs. If a CA doesn't comply with the standards, it will be harder for the CA (or its parent, if it's an intermediate) to be trusted by browsers.
https://cabforum.org/members/
You'll see that that's far from including all root or intermediate CAs that are active on the web.
But the major browsers have incorporated the Forum's standards directly or indirectly into their root certificate programs. If a CA doesn't comply with the standards, it will be harder for the CA (or its parent, if it's an intermediate) to be trusted by browsers.