While your question is absolutely valid, and makes perfect sense - it can be the catalyst for threads going on for days, if not weeks - which I've also seen turn in to flame wars, depending where you go on the internet.
In the end, unless there is a real and obvious reason - such as security - to use one browser over another, or a=even avoid a particular browser entirely, I would respectfully suggest that it's just a matter of tase.
I go back to Netscape 4, which I *personally* found to be preferable to the versions of IE which were available back then. While I have always updated to the latest versions of IE - and they have certainly taken many steps to add layers of security since then - I find Firefox provides me with the options which allow me to configure it to my own personal tastes.
I can download YouTube videos (or just the audio portion) directly with Firefox thanks to a couple of add-ons.
And yes - some of my add-ons are simply eye candy - a means to adjust the GUI to my liking - but, why not ?
Unlike Lighthouse, I am disturbed to learn that some of my add-ons could be tracking my browsing activity, and have already taken some steps to shut those holes.
I posted the link to Martin's article because I figured there are others here who also use Firefox as their browser of choice, who might be unaware of this development - just as I was.