Like I said, Facebook has the social graph and no one uses their payment system b/c
1 - you pay with credit cards and they're super entrenched and you don't forget your credit card like you may forget to bring enough cash
2 - at least personally... I rarely find I need to give my friends money in the US. It happens once in a while.. but not every week like in China
But the specific points you raised mostly don't help us understand what's going on. (1) is incorrect, (2) applies even more in the US than in China, (3) is just wrong, (4) is irrelevant as people have bank cards.
I say (3) is just wrong because: (i) WeChat doesn't facilitate paying for each others' meals; it only helps when splitting the bill, and (ii) red envelopes weren't a daily thing before WeChat. They were only for special occasions.
Anyway, I think we can agree there are multiple factors that got WeChat payments to where it is. I'm not sure I have any additional insight :)