Because you can access it for free? As it was the case from the first day LLMs became a thing in public consciousness?

Or did I miss the change, and ChatGPT, Claude and Gemini no longer have a free tier anymore? And then the next tier that costs peanuts for anyone in the west, that gives you more access to slightly fresher models?

Exactly. Companies like Anthropic do not want open access. See their FUD against "distillation attacks"