I think part of the reason nobody tests for it anymore is just because web standards have largely gotten so good. I don't often test in FireFox these days myself largely in part because it just hasn't been a problem in years.
I'm old enough to remember the days when every change I made I had to roll through multiple versions of IE all the way back to 6, and different things would be broken in different versions.
Transparent PNGs using CSS filter:progid:DXImageTransform.Microsoft.AlphaImageLoader is my shudder. Flat design would have made life so much easier back then.
I'm old enough to remember the days when every change I made I had to roll through multiple versions of IE all the way back to 6, and different things would be broken in different versions.