When I worked at a telco in Afghanistan in 2014, Facebook was basically its own utility - SMBs and individuals used Facebook (and their precious cellular data) almost exclusively to message each other and conduct business. So much so that the most popular consumer/retail plans for Afghans were "Facebook usage plans" giving you X amount of data per month to be spent exclusively on Facebook. Amazon/google have little to no power over there, facebook has a ton. Ditto whatsapp.
I think you'll find this is true for almost any country where social ties are stronger than the US, and biz is newer, or built around mobile/face-to-face transactions - fbook is much more important than it is here as a photo feed and news consumption hangout.
That said I agree for the US case and deleted my facebook ~2 years ago :)
Also, I think your second point contributes to this: mobile is huge in the Philippines, they send more texts than any other country. And on top of that, social ties are a lot stronger than those in America, especially familial ties, with many siblings, cousins, etc.
Facebook has zero-rating on mobile in the Philippines.
When I used to work in the restaurant industry, my boss would order wine from one of the wineries using Facebook messenger. There are also social data plans that give you cheaper rates for Facebook, Snapchat, and some other services.
I'd also say that a lot of people I know exclusively get their news from Facebook and it's also very important as a photo sharing application.
From what I've been hearing from internal teams, Facebook is hoping to take some of email's pie. I expect to see them pushing more people to use Facebook Messenger in place of email. And they're working on new types of ads that interface more with the Messenger. E.g. start a conversation with a company instead of taking you to their web site after clicking the ad.