Nothing.
They have their ‘niche’ market, and people often won’t change unless all their friends do too.
Being ‘free’ but playing all kinds of data-mining games with their followers to fund the platform holds much appeal to those who just want something simple that doesn’t cost them anything. If they aren’t savvy enough to use FB Purity, or Add block etc., they will grumble, but most likely continue to stay there, and be advertised at remorselessly.
Cheers!