STT (driven by machine learning models) has been part of the academic research field called Artificial Intelligence for decades.

Probably because AI is a misnomer. Machine learning is a better name, but even than it is pretty lacking.

What is generally called AI in common speech is pretty much a class of non-linear statistical models which require some training to generate weights which are than used to fit the model. Most people that know anything about statistics knows this, so it is fine actually. Misnomers exists in all industries and all science, and we just deal with them.

I believe this article is about STT, not TTS

AI does a better job of STT than the other techs.