Earlier quoted context omitted.
There didn't use to be any rules to play by. Official "front door" APIs are a modern phenomenon. They started being offered, and rugpulls were rare, so we got complacent and started using them rather than reverse engineering first-party APIs.
In the one non-open-source company I worked at, the first-party API was an extension of the public API. Some methods took additional internal-only parameters if you were using one of the official app IDs, for example. Some returned additional fields in responses. A bunch of additional internal-only methods also became available. I mean, if you have a public API, it makes sense, engineering-wise, to build your interna…
Old reddit for example uses the reddit API essentially directly. now with new reddit, there's been a split, and it looks like from my count that reddit is currently supporting like 7 different APIs internally, parts of them all used in various different places. The reddit API is pretty functional and most of what anyone would ever really want to do was already supported in the API (and therefore available basically with few current restrictions).
Few of the actual undocumented/internal APIs on reddit are all that interesting.
[1]: https://www.reddit.com/r/redditdev/comments/14nbw6g/updated_...