Bing is the default engine in Edge which is the default browser on Windows. There’s a huuuge demographic who doesn’t care enough to change either of those.
Also, Bing profits from other search engines using their results as a base. DuckDuckGo, for example, uses Bing as their primary source for search results. And in my experience is better at it than google, these days.
I've personally moved to Bing from Google. Partly because it's annoyingly the only way to do web searches from the start menu, But also because it's much more flexible with AI compared to Google's new AI Overviews (The engines vice president actually tweeted about being able to disable Copilot in response to Google's new AI).
I personally like how Bing presents information better, but it still has quite a few problems. Especially around relevancy, and it's image search isn't the best if you're looking for anything that isn't a photograph.