Because I agree with it.
Oh, the joys of firefox, until you have to deal with an internal site with old code that has sat there running fine, doing its job for years, but Firefox can’t use it. Oh sure, there’s a point that the site should be upgraded, but right now, it costs zero dollars to maintain, while upgrading it solely so that another browser can use it will cost...not zero dollars.
An argument in defense of not Firefox just for the sake of Firefox. And it's true. It's a shame, and makes my work more difficult, but what can you do?