I don’t see wtf it does aside from be a middleman
It would allow people around the world, many of whom are unbanked and have no access to a ‘stable’ currency like USD or a peg, but who have smartphones and use facebook/whatsapp/instagram daily, who don’t have the technical know-how or on-ramps to use real crypto or neat gadgets like hardware wallets, billions of them, to send money to each other rapidly, cheaply and securely within a platform they are already on board. That is entirely why facebook is doing it. The members of the little ecosystem you occupy, where this obvious value proposition (a fundamental one of real crypto too) is beyond comprehension, are not the primary target market.
What it does, precisely, is give other people access to the basic money services you have the privilege to take for granted.