The only reasons I've ever put effort into Firefox support in my software was A) I find it helps push me to write towards standards better if I include multiple browser engines, which makes it more likely I'll support Safari without extra effort, which is difficult for me to test on because I don't daily drive any Apple devices (works about 80% of the time), and B) to avoid the shit-fit I would receive if I ever posted it as a "Show HN." It has never come up as an actual user requirement.