broken record ik but it's very unfortunate that this is set in past tense when PDS -> app service proxying is key to actual use cases of altering undesired app behavior today (e.g. age assurance circumvention, feedgen sponsored item elision, etc)
So anyway, one of those early ideas was that by proxying through the PDS we created similar benefits to having an extensible browser. Rerouting or blocking requests to alter application behaviors, things like that. The logic was to act as a political backpressure to the applications