Seraphor already covered most of it, but the other point about "But 3rd Party Apps!" is related to the data actually being used to generate the display. All a 3rd party app has to do is read the output with no real QA or technical requirements. In other words, they're basically just reading a text file already output by the game. An in game solution would require reading both the input and output data flow, and would have to actually be tried and tested in QA to ensure basically 100% accuracy. There's a lot more going on there that 3rd party apps don't have to deal with.

Would it be possible? Yeah. Is it considered worth doing? It seems not.