The problem is that many wouldn't believe it if they were told (i.e. "this is what big tech wants me to think"). This is essentially what happened when Facebook and Twitter informed users that had interacted with suspected propagandized content.
Particularly after this current purge, social media companies have lost most of their authoritative credibility. Combined with a political culture that embraces wild conspiracy theories, you'd just be adding fuel to the fire.
Particularly after this current purge, social media companies have lost most of their authoritative credibility. Combined with a political culture that embraces wild conspiracy theories, you'd just be adding fuel to the fire.