You are right that not all Bullshit Jobs have the idle time I'm talking about but enough to create this culture. But I can't say it better than he himself:

One might imagine that leaving millions of well-educated young men and women without any real work responsibilities but with access to the internet—which is, potentially, at least, a repository of almost all human knowledge and cultural achievement—might spark some sort of Renaissance. Nothing remotely along these lines has taken place. Instead, the situation has sparked an efflorescence of social media (Facebook, YouTube, Instagram, Twitter): basically, of forms of electronic media that lend themselves to being produced and consumed while pretending to do something else. I am convinced this is the primary reason for the rise of social media, especially when one considers it in the light not just of the rise of bullshit jobs but also of the increasing bullshitization of real jobs. As we’ve seen, the specific conditions vary considerably from one bullshit job to another. Some workers are supervised relentlessly; others are expected to do some token task but are otherwise left more or less alone. Most are somewhere in between. Yet even in the best of cases, the need to be on call, to spend at least a certain amount of energy looking over one’s shoulder, maintaining a false front, never looking too obviously engrossed, the inability to fully collaborate with others—all this lends itself much more to a culture of computer games, YouTube rants, memes, and Twitter controversies than to, say, the rock ’n’ roll bands, drug poetry, and experimental theater created under the midcentury welfare state. What we are witnessing is the rise of those forms of popular culture that office workers can produce and consume during the scattered, furtive shards of time they have at their disposal in workplaces where even when there’s nothing for them to do, they still can’t admit it openly.

David Graeber, Bullshit Jobs 2018 (p. 382 of 895 in my ebook version)