People tend to have multiple browsers. You might have FireFox installed but still not be aware why you should use it over other browsers on your computer.
This is a very good reason to put this kind of page in. For less computer savvy people, they may vaguely know "if I click this fox icon it takes me to the Internet and so does this colorful circle and this blue swoosh, so it's all the same" but when they accidentally open one they use less often, seeing something like this might push their preference a little for which one they open
i do the multiple browsers thing, but it's firefox, firefox developer, and librewolf (i also have a seamonkey and a waterfox on one system). and they can all run at the same time without conflicting with another.
the few instances where i need a chromium-based one, it's a fresh 'install' of a portable 'alternative' like vivaldi or opera from portableapps (or via appimage on linux) and then deleted when i'm done with it.
Oh that makes sense. I just assumed people who have Firefox would know stuff like that since Chrome is usually the one people know about but yeah it could have already been in the OC or they just searched for a different one randomly.