Just read these comments to understand why
Take a look at the comments above. It’s all mildly technical stuff that casual web users don’t give a shit about. The UI is crap, this bit doesn’t work, that bit is flakey, I needed to install x to get y working. You all no doubt work in tech and have an underlying interest in it. The majority of people don’t. That’s why no one gives a toss about Firefox apart from the tech community. In fact most users probably never heard of it let alone could be bothered to install it.
I open my phone and safari works. I open my laptop and chrome or edge work. You’re lucky if any casual users even install Adblock. Most don’t even know the name of the browser they’re using, they just click a desktop shortcut…