Wikipedia rabbit hole jokes aside, this feature makes a lot of sense. It allows you to research a topic from a single Wikipedia page, rather than having to open multiple related pages in new browser tabs and move back and forth. Page previews display the first few sentences of the corresponding Wikipedia article, allowing readers to determine whether the topic is relevant to the subject they are currently researching.
The Wikimedia Foundation did extensive testing before deploying page previews to the general public, and they found some interesting (and extremely encouraging) results. For one, a negligible percentage of people disabled the feature, which means it wasn't intrusive. But perhaps most interestingly, the number of regular page views on the site slightly decreased. As the Wikimedia Foundation notes, page views are an important benchmark, but they aren't the end all be all. "For the Wikimedia Foundation, success is based on how we're able to fulfill our free knowledge mission and make the Wikimedia sites more useful, relevant, and engaging for people around the world, even if it means our pageviews might go down as an effect," the blog post says.
So, if you do love those Wikipedia rabbit holes, page previews won't prevent you from embarking on that kind of journey. But they will streamline your Wikipedia experience, helping you research the topics you're interested in without sending you on tangents that take you away from what you're trying to accomplish. If you have any feedback on the feature, you can leave a note on the page previews discussion page.