It's from Google, they deprecate things every 6 months including APIs your app is using, if you don't follow your app will be down pretty quickly. AWS nearly never do breaking changes.
AWS GameSparks.
Being shut down end of November and bringing down one of my favorite games with it, because the devs were foolish enough to believe what you believe, that AWS sticks with its products.
It's AWS page says Preview, meaning it has never gotten to an official stable release. It's like using a beta/rc product, there is an explicit warning this is not the final version and it might not get anywhere.
But since Firebase is from Google now, anyone who worries about Google deprecating products have equal worries whether Firebase is based on GCP or not.
Outside of HN, I find developers (at least in Europe) often prefer GCP and businesses have full faith in the offering because of the Google stamp.
For Azure I have yet to find a developer who likes it, but businesses are drawn to it due to the packaging with other Microsoft services (eg you buy office 364, teams, Active Directory and Azure together in a Enterprise package) and businesses have full faith in the Microsoft stamp of approval.
Same, of all the people I've interacted with, it's AWS and GCP which are liked (AWS mostly for features, GCP more for UX/DX), Azure is at best accepted and the only reasons anyone uses are "we were already a MS partner/shop".