I've run into a few restaurant sites whose ordering pages just do not work properly (or at all) in Firefox. Also webgl2 performance is unfortunately still much better in Chrome vs Firefox; as an example, FoundryVTT (virtual tabletop software) works fine in Firefox but is a stuttery mess IME (though it has improved slightly in the last few years).
I'd bet my bottom dollar those websites still work in Edge, Chromium and Brave. The alternative to Chrome is not Firefox, it's just Not Chrome.