A huge chunk of FreeBSD and Linux development is done by salaried workers who want specific functionality. Microsoft is the biggest contributor to the Linux kernel for instance. I don’t think there is much apetite for that in web browsers. Linux is an industry leader in the server space, adding features to it that complement whatever you make for profit is a good move. Firefox is unfortunately barely relavent in the browser space, if your product relies on Firefox exclusive features it isn’t going to go well for you.