In the early days, Twitter used to have a very open and friendly API. It's a big part of why users and third-party devs (I was both) loved it. Same thing was true of Facebook and Reddit.

Over time, they shut down their APIs (or charged huge fees) in an effort to intentionally kill off third-party clients and services.

A key goal for Bluesky is to "lock open" the network and the API so that it's impossible to reverse the decision.