Yeah, there's a very simple reason: the FAANG acronym was coined around 2013 when Microsoft was still in a rut, Ballmer was still CEO, and their stock was still down from its dot-com bubble peak.
So this is specifically a Silicon Valley / Hacker News thing (notably relevant to lifestyle and employment issues).
The rest of the world has been using GAFAM instead, even before 2013. (I've also seen "the big 5" sometimes.)