I'll give the straight answer to what I think is a rhetorical question.
Firefox for Android syncs with Firefox desktop so there's a shared history and I can easily send tabs from one to the other. It's also easy to copy proper URLs instead of shady shortlinks that often contain affiliate codes and trip spam filters. Finally, I don't want to give Amazon a foothold on my devices; the browser has a stronger sandbox than native apps do.
Firefox for Android syncs with Firefox desktop so there's a shared history and I can easily send tabs from one to the other. It's also easy to copy proper URLs instead of shady shortlinks that often contain affiliate codes and trip spam filters. Finally, I don't want to give Amazon a foothold on my devices; the browser has a stronger sandbox than native apps do.