Historically, there have been several approaches to including special pages as pageviews:

• Erik Zachte's initial definition included all special pages
• The "new" pageviews definition introduced around 2015 blacklisted a specific set of pages used for programmatic activity and "user actions" (such us "logins") ( BannerRandom, HideBanners, CentralAutoLogin, MobileEditor, Undefined, MobileMenu, BlankPage, UserLogin, ZeroRatedMobileAccess)
• Since July 2019 (T239672), only three whitelisted special pages have been counted (Search, RecentChanges, Version)

However, none of these has been completely satisfactory, and we should come up with a consistent, stable rule. Some considerations:

• If a special page is excluded from pageviews, that means its view counts will not be retained past 90 days or available through the pageviews API. This can hamper analysis; for example, during the Recent Changes filters project, the Collaboration team looked at pageview counts for RecentChanges.
• In some cases, including special pages has had undesirable privacy implications (T239672) or caused spikes in pageviews unrelated to actual content consumption.
• Some special pages are automatically called by MediaWiki when certain actions are taken (e.g. CentralAutoLogin), and these should obviously be excluded. However, the large majority are only accessed through explicit user action in order to change settings or access information.
• Viewing a special page with information about site content like Watchlist, MediaStatistics, or Redirects doesn't seem fundamentally different from viewing an article talk page, which is counted as a pageview. Similarly with viewing special pages with user information like UserGroupRights or AutoblockList and viewing user pages.
• add yours!

You can find a full (?) list of a special pages at Special:SpecialPages.