Because most of these things are not multi-trillion-dollar ideas. "We found a way to make illustrators, copyeditors, and paralegals, and several dozen other professions, somewhat obsolete" in no way justifies the valuations of OpenAI or Nvidia.
That's right, but there's more. When you think about the cost of compute and power for these LLM companies, they have no choice. It MUST be a multi-trillion-dollar idea or it's completely uninvestable. That's the only way they can sucker more and more money into this scheme.
This does have value.
Though if the bubble(?) bursts and Nvidia starts selling fewer units year-over-year, that could be problematic.