I think the problem is that George doesn't really appeal that much to a lot of teenage girls though. He has the personality of a cardboard box, is a walking PR mouthpiece, is good looking but not in the Disney prince way that Carlos is or the accessible boyband way that Charles is or the hot older man way that Alonso and Lewis are. He doesn't have the approachability and charisma of someone like Lando, the easy charm and appeal of someone like Alex, or the humour and relatability of someone like Oscar or Yuki. He doesn't even have the somewhat-grubby-bad-boy-your-parents-would-hate-you-to-bring-home appeal that Pierre does. He's basically a big dull plank with chiseled features, a marketing persona that feels like some kind of AI experiment by the Mercedes PR department to create their perfect mouthpiece, and a somewhat unappealing on-track personality. He's also clashed somewhat with his wildly popular teammate and it's clear they don't really have that much love for each other despite how the Merc PR department try and paint it, so they can't play up the whole bff teammate social media thing that works for other teams.
His personality may be very different in real life and he might be a lot of fun but his public persona is not. The only time he really seems fun, relaxed and relatable is when he's is doing press stuff with people like Alex and/or Lando, or when he was doing the Twitch Quartet streaming stuff during lockdown, when more of who I suspect is the real him comes out. Carmen, however, does seem to appeal to a lot of that teen/early 20s audience who are obsessed with the drivers' relationships - for some unknown reason they see her as relatable and someone to look up to. My guess is Merc have realised they get better engagement featuring George as part of the "George and Carmen the ideal couple" package deal than they do with him on his own, so they shoehorn her into their social media wherever possible. Williams did the same thing with him when he was there.
(believe it or not I don't actually mind George and quite like him sometimes, but I can completely see why he has very little marketability on his own especially to the kind of audience that comes with social media)