I had a ceo type person ask me just last week if we were testing on firefox and I kinda did a double take.

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 mean, I don't object in principle, I in general consider this to be "doing a good job" that we all strive for, but in this particular case it was a "line of business" app with like 500 users so I genuinely hadn't even considered it. We'll see if it comes up later!

That entirely depends on who those 3% are and how much revenue they bring. Back when IE6 had 3% that was reason enough to keep supporting it

IE6 was already announced dead by Microsoft when it reached so tiny market share, you are forgetting IE got several versions up to 11, before being replaced by Edge, followed by Edge Chrome, later rebranded as Edge.