Certain places do, actually. That's why lots of enterprise software was stuck having to support IE just a few years back (and probably still in some places that haven't caught up).
I've seen demands towards certain features working on Edge/Chrome in particular even if it would break something in Firefox, which might be preference of the end users but also corporate policy towards using known software in certain places.
I'm sure that you're still likely to run into plenty of environments where something like Edge might be the only allowed browser.
Yep, and talking about Jira, they only ended that support in March 2020.
And wow, according to Wikipedia, Microsoft still supports Internet Explorer on some non-consumer Windows flavors. Today. I find that actually pretty stunning, must be a huge liability to be running web-apps that breaks on non-IE, because that can't then be the only aspect at which it's still stuck in the stone ages.
(Nothing against ankitpokhrel and this great tool, just making a point in a slightly sarcastic way)
I have done that multiple times. It's not very time demanding, because the working code is there, and all you're doing is essentially deleting code you either don't understand, or don't need. At the same time, you're reading the code you do use.
I am the customer of our IT, I don't know why it should be any other way. It's noteworthy though that I don't work in a tightly regulated sector.
You may also be able to get 3rd party insurance for this.
All software, including open source, technically needs to get approved by a security team.
They only enforce it if you run windows, though.