[diegoperini]

User-base has no importance, dev-base is what matters here. If Mozilla sends a letter to developers, chances are those people already stumbled upon MDN multiple times when they looked for answers to web development related questions.

[chrisseaton]

Why would developers care about a browser that their users don't use?

[jmcs]

Can you imagine if retail stores where made in a way that 3% of customers couldn't use them?

[chrisseaton]

If there's no law saying they have to support those 3% of customers, and supporting the 3% costs more than the 3% bring in, then yeah they won't bother.

[diegoperini]

Because if "Firefox/100.0" reveals a bug, the bug may also trigger when other browsers introduce a similar change.

[kelnos]

All the web developers I know use and test on Chrome. If they test on Firefox, it's as an afterthought.

[edoceo]

Hello! Know you know one who builds and tests on FF.

[moltar]

I use FF as a daily driver.

[h0l0cube]

I also use it for developing and use its developer tools. If it works on Firefox, there's maybe a few CSS tweaks I need to make when I test on other browsers