I mean, they exist in much less of a form. It's trusting 1 entity vs literally everybody, including people intent on being bad actors. You also have to have less trust because you're operating in a more or less known environment.

The network bandwidth will be a real problem regardless. Latency too. Single digit millisecond scale database roundtrips are awesome. 50-100ms would be just terrible. If that's a fundamental limitation then applications can only get worse, not really better.

Overall, what fundamental problem are these solving? If they aren't solving a real pain point with a worthwhile cost, uptake is going to be nonexistent.