I agree with your point about it being weird to auto-add search engines that aren't Google/Bing/Yahoo/DDG. But I will say that (while it does randomly get frustrating) the lack of automatically adding search engines is a plus for non-tech users. I say this due to the absurd amount of client computers I work on. Obviously them somehow installing extensions that change the search and home pages will still happen (and does).

But Chrome is one of the worst (though Safari is apparently super susceptible to really nasty search hijackers/re-directors that get in deep af) about scamy/spamy search engines getting added and setup (many times even lists the name of the search in the selection list as being one of the big ones including Google). Also see massive lists of such engines ready to add as "discovered". Where as it is super unlikely for FF to be hit by non-extension engines being set as defaults. It is of course impossible to fully protect everyone, and it is dumb to stop users that are vigilant of this stuff from being able to take off the training wheels.

I am just saying that from a dealing with this really specific situation I see everyday FF is doing well. Also being fair I find the DDG Bangs (and the same feature on Brave Search) to be better than just adding all the search engines. I just wish they (Mozilla) would make an extension that could do the same thing. No need to install really more than one default if you can just add a small variable at the beginning.