The content is available to search engines, and they are highly optimized for SEO, so they show up high in search results. So users expect by clicking the link in the search result they can see the rest of the content. Then you get hit with a paywall.
The news sites return different content to search engines than they do to browsers. Which means you get a different site than what is shown in the search preview, specifically a paywall page.
I would be a lot less annoyed with these paywalls if they didn't rank so highly on search results, or at the very least indicated they were paywalled on the search page and were easy to filter out.