There is a proposal for that too: https://site.spawning.ai/spawning-ai-txt but it's wholly unclear if AI companies actually do something with this or if it's just wishful thinking...

Some AI companies follow robots.txt (OpenAI and Google, for example) but others ignore it. There's also other limitations around using robots.txt to sole this problem: https://searchengineland.com/robots-txt-new-meta-tag-llm-ai-...