Firefox

I'd guess that:

• Google is a bigger brand that attracts many people as a lot of them are already using some of the company's products
• These other products are well integrated with the browser: browser history is shared across devices along with passwords and extensions
• Google advertises Chrome in the Google Search, it's a default search engine even in Firefox

Most people are not tech savvy and/or privacy-oriented.

Why make the effort to switch to Firefox, if the browser that came installed with your device works?

Or, more realistically, people don't even grok the concept of a web browser.

Back when IE was on top and Firefox was the best browser, firefox started to put a lot of bad updates, then chrome came, it was faster and firefox started to lose its marketshare, for while firefox only peformed well on linux, by the time quantum came out and it's performance was good on windows again, Chrome was already the new IE, but Google is way better at managing this leadership it than Microsoft ever was, the only technical problem it has is devouring RAM.

In my opinion, gecko being so tied to the browser is also a problem. There's a ton of browsers using Blink, that gives google a lot of control over how the web will evolve. Having other browsers using gecko that aren't Firefox forks would be great.

I've used Firefox for years and I love it on Android, but on my work laptop (MacBook) I really enjoy using Arc. The vertical tabs let me organise things better, the spaces let me isolate tabs properly in a visually pleasing way, and I don't really care for extensions on desktop as I don't really browse much outside of work. I also prefer chromium dev tools, though it isn't that bad to switch to Firefox's dev tools.

If Firefox adopts few features from Arc, both in form and function, I wouldn't mind coming back. I know sidebar exists which lets you have vertical tabs via extensions, but damn Arc does it the best so far, natively!

Edit: oh, another reason was lack of background blur effects for Google meet. It's coming soon I think (I filed it on bugzilla), but damn it was needed like 3 years ago.

One reason is that if you use Gmail, every two weeks appears a "y u no use chrome" nag popup that can't be permanently dismissed

Websites glitch out more often on Firefox. I had my favorite Mastodon instance not letting me scroll back up because of some weird jittering bug that only applies to Firefox for some reason.

For me, until all below are supported Firefox can't be my primary browser.

1. PWA not supported and only possible with FirefoxPWA. I can't rely to anything but native, Mozilla could break FirefoxPWA any time they want.
2. I use my browser for my multimedia needs and I use my own Emby Server. Firefox doesn't support mkv container and the most important it desn't support HEVC. Please do not tell me about HEVC royalties and how much Mozilla would have to pay MPEG-LA. Chromium based browsers have enabled hardware HEVC decoding and they pay nothing to MPEG-LA because the royalties have been already payed by my graphics card. Mozilla simply doesn't care.

If you've been on youtube for the past 6 months or so, there were a lot of OperaGX sponsorships given to large creators and a decent majority of people have used it, liked it, and started recommending it to others via youtube comments.

There's also the fact that chrome is the browser that, at least here, is the most well known at this point and is usually preinstalled on school computers, so this builds up familiarity.

And probably a smaller reason why is because mozilla itself - it hasn't been that great of a company and the firefox over the years has gotten somewhat worse and worse.

I use Firefox. The only thing I don't like about it is that Duck duck go isn't a terribly accurate search engine compared to Google.

On my private PC I use firefox on my work laptop I use chrome. The gmail and gdrive integration just makes it easier.

Still on my private I have to switch to chrome for a few things because it just has more storage

Because the U.S. government used the 2001 Microsoft Internet Explorer Antitrust hearings to blackmail Microsoft into government servitude: implanting NSA backdoors, not patching vulnerabilities, disabling system administration tools, constantly hiding or moving useful features. Remember from the Snowden leaks that the NSA's favorite prey is the System and/or Network Administrator who holds all the keys? But what about the guy that makes the keys, wouldn't he be the biggest prey?

I still miss the print a webpage to pdf on mobile firefox.

I didn't find the performance gap really high when I switched from Chromium to Firefox. Even on my shitty old laptop, Firefox works fine. I have to admit though that it uses way too much memory.

I do agree with your 3rd point though. History has taught us that defaults matter a lot. Firefox isn't a default anywhere apart from linux distros and FirefoxOS was a failure.