It absolutely is a technical necessity. You could build a model from scratch today without doing the same thing. And every model attempting to train on AI generated output degrades into nonsense almost immediately.

There’s a reason Reddit is making millions of dollars letting these companies mine their human generated content. You think OpenAI or anyone else would pay for that if they could just cyclically train on AI generated content???

> attempting to train on AI generated output

I said nothing about that. Good synthetic data does not (typically) involve ML algorithms. Although that might be changing.

I'll politely suggest that you go read the literature before engaging further.

Reddit, Twitter, and similar are valuable because the data covers current events. Their content makes up a reasonably comprehensive timeline of the world at large. You don't need that to train a barebones functional model but it's certainly useful in order to train a knowledgeable one. Regardless, if they're charging for access it clearly isn't piracy so it doesn't seem like your original objection would hold any water in that case.