Facebook users are perfectly capable of reading websites and sharing them on Facebook using a URL. It’s not necessary for bloggers to embed Facebook’s code and logo on their website to enable this.
Sadly, a vast majority of Facebook users have know idea of what an URL is. Big tech is even doing everything it can to make/keep people ignorant of what an URL is, like Google reformatting its result page to make URLs look like breadcrumbs, or Safari and Chrome hiding more and more of the url in the address bar...
But in that case, chances are they arrived at the article from a link posted on Facebook. So they wouldn't need to click the share button on the site if they wanted to share it.