This site has had advertisements enabled for some time now, as the team has been expanding those to non-technology-related sites, of which this site happens to be the largest. On such sites, users with at least 200 reputation have some of those ads suppressed by default (but can re-enable them in their user preferences).
However, the privilege page on reduced ads doesn't show in the list of privileges on this site, and users don't receive privilege notifications when they earn 200 reputation, as they do on other sites where the page is visible.
Per this Meta Stack Exchange post, this is considered a bug:
The privilege exists everywhere. But on most sites, it's hidden and notifications for earning it are suppressed. Doesn't make much sense to tell folks about a privilege that doesn't actually do anything.
That said, if we forget to enable this on a site that is hosting (and therefore suppressing) such ads, don't hesitate to post a bug report.
This site falls into that last category, and this is the bug report.
Also, see this other global meta post that clarifies that enabling advertisements and enabling the help page are two separate processes, and there's a history of the team doing the former but not the latter.
This is not a duplicate of What does the "see reduced ads" privilege mean?: that was filed back when ads weren't shown on this site, and the privilege page wasn't being suppressed when it was supposed to. However, it isn't supposed to be suppressed today.