The report comes from StatCounter, which suggests Bing remains the second-most popular search engine with a 6.89 percent market share, while Yahoo, DuckDuckGo, Yandex, and AOL languish...
Why would they keep it on? Sure, they will continue to collect data for their AI, but I'm pretty sure they are happy that they don't want to keep it on if it might drive you to use other search engines. And turn it back on after a few versions of optimization
DDG uses Bing results but doesn't serve you the ads on AI features.
I've found as people use DDG, Bing has become more and more useable day-to-day. Used to only really be good for porn, because people didn't want to Google it but felt comfortable using Bing. Now it's getting more relevant results as people use it to troubleshoot and research, etc.