Since Mozilla and Firefox respect your privacy and don't track you or store information about you like other companies/browsers (Microsoft/Apple/Google), we can't tell that you've installed Firefox for Android. So this notice will display sometimes, even though you've already installed Firefox for Android. It's a mild annoyance. But we think the trade-off is worth it. Mozilla is a non-profit organization on a mission to make the web a better place. One of the 10 Mozilla Principles is that "Individuals’ security and privacy on the Internet are fundamental and must not be treated as optional." You can read more about the 10 Principles here: https://www.mozilla.org/en-US/about/manifesto/