why are the visitor/users of most websites with the cookie popup forced to “Accept and Continue” without an option in form of a button/link to Decline
There often is an option to decline, which either is a link to Google or the sentence “leave the site”. This is in almost all cases no opt-out, as such sites created (even 3rd-party) cookies, which are not deleted when you leave the site. So e.g Google analytics loaded at site B knows your were at site A, even when you immediately left site A when seeing the banner telling you “To opt-out leave the site”. Which is not compliant to the law, but I do not know any case where someone got sued over this, either.
and is this right by the laws guiding cookie usage.
It is not. But before GDPR, only few countries had enforceable laws covering this and with GDPR many sites still think their “cookie banner” covers the legal issues. You may have noticed, that some of the big players added GDPR-walls instead of banners, because the new law includes costly penalties, so they do not want to be the first one to be sued for now respecting the law.
I asked for more details on GDPR walls on law.stackexchange.com, maybe you are interested in the question and the answers there.