Sadly Firefox has been out of our browser matrix for several years now, it is only taken into consideration by FE teams when the customers explicitly ask for it being supported.
I also use because I care, but at 3% hardly any business does any longer.
I think I understand where he's at. If your web site has compatibility issues with smaller browsers like Firefox at 3%, Opera at 2% etc. then you could be losing out on 5% of your sales. If you were to approach any CEO and ask if they'd be interested in an initiative to increase sales by 5%, they would most likely express an interest.
there is good chance whoever site didn't worked for will just switch to chrome for that site. I did that few times.
We have "any browser above 5% market share" in deals with our clients. So FF testing is not even required
I had a ceo type person ask me just last week if we were testing on firefox and I kinda did a double take.