I think it certainly helps that FBM is the communication standard in Australia - the only SMS I get now are sent by computers, and iMessage never really caught

I think it certainly helps that FBM is the communication standard in Australia - the only SMS I get now are sent by computers, and iMessage never really caught on. This gives some lock in, even if you don't actively use the website or the app. It is assumed that if you want to contact someone after meeting them you'll just look them up in messenger. Yours is an interesting perspective because I tend to assume that people on HN who say "just call your friends" are less social and don't have as many people they want to catch up with. Honestly events and groups are the real utility - there's where everything I care about happens on Facebook itself (aside from Messenger - which is good, but we would be doing the same thing elsewhere if it didn't exist). Though the feed is still terrible - I keep my friends list relatively trimmed (~200 people) and it's still rubbish.