These default search deals are only on new installs though. How often will those users reinstall Firefox?

No. You are wrong, either confused or lying. These deals are a revenue share for ad engagement on search results. Stop the lying.

I think you are replying to the wrong person?

If I set my search engine to DDG and Firefox has a deal with Google, then my browser is going to change my search engine to Google? Of course not. When you install Firefox it defaults to Google. In the past when Firefox had a deal with Yahoo it defaulted to Yahoo.

Are you suggesting that is incorrect because all of that happened?