On some sites, ads are shown above the question ("top leaderboard"), beneath the question ("mid-page leaderboard"), and in the sidebar; these are the ads that are affected by the "reduced ads" privilege. However, ELU doesn't have these ads so there is no privilege to remove them. (It's also relevant to note that meta sites never have ads, even if the main site does.) See my answer here for more information about advertising.
It's possible that we could get ads in the future. Some sites right now are in the process of getting ads, even though they're not technology sites (which is where the ads have been up to this point). The process for those sites will go something like this:
- First, there's a testing phase, which will be announced with a meta post. During this phase, it seems to be just Stack Overflow for Teams ads that are being shown. It also doesn't seem to be possible for advertisers to buy ads for sites that are testing advertisements.
- According to this post, the reduced ads privilege will likely be available on those specific sites after they finish doing the testing. (Probably when it becomes possible for advertisers to buy ads.)
- In case it's not obvious, the thresholds for privileges are based off your total rep, so you will be able to get the privilege immediately if you have 200 or more rep on that site. (I don't remember when this site last got new privileges, but Stack Overflow briefly had new privileges with Documentation that made this obvious.)