Bing will be adjusting the SERP format and no longer showing ads on the side.
This will start on 3-26-18 (even though they sent emails on 4-6-18 telling us about it) and will be getting tested in international markets soon after.

As part of the constant evolution of the Bing search engine results page (SERP) to provide more value for our users and our advertisers we are regularly evaluating performance and quality of our ads, including ad position on the SERPs. In keeping with this commitment, we have decided to remove sidebar text ads on our Bing inventory in the United States on March 26th, with international markets testing to follow at a later time..

Here are more specifics around the changes we are rolling out:

• Text Ads will no longer be served on the sidebar, while Product Ads will continue to be served on the sidebar.
  
• Bottom of the page (BOP) ads increase from 3 ads to 4 ads. Moreover, BOP ads allow for richer ad formats, which sidebar ads didn’t.
  
• This change applies to the Bing SERP only. No impact for syndication partners including Yahoo and AOL.

Source: [advertise.bingads.microsoft.com...]