Microsoft Corporate Vice President Yusuf Mehdi shared the details of the decision in a March 29 blog post about Bing’s ability to “drive more traffic to publishers.”
After a long talk about how the new Bing “…helps better serve people’s search needs with new capabilities,” the post mentions Microsoft’s desire to share money with site owners (publishers):
We’re also exploring the possibility of running ads in chat to share ad revenue with partners whose content drives engagement in chat.
It appears that this feature is not yet available to all Bing users. Debargya Das, a founding engineer at Glean, captured what the ads currently look like and shared it on Twitter.