The last time I checked (this may have changed), Firefox also tags the default search engines with URL query parameters indicating that the search came from Firefox. When I tried to change this it would not let me edit the default URLs. I had to add entirely-new versions of Google and DuckDuckGo, with custom names and stripped-down URLs in order to avoid the tagging.

No doubt it is revenue-related, but it's also a privacy problem.

> it's also a privacy problem.

Can you describe how? What information is that query parameter providing to an attacker that is not being provided in 50 other ways?

Your question is assuming they're not already locking down as many of the 50 other ways as possible. Yes there are other bad things but that doesn't mean we should add #51 to that list.

OK, so it's not actually a privacy problem. Thanks.

I suppose it tells them you searched with the address/search bar instead of navigating to the search website. But I'm not sure why you would care about that.