Robots.txt has failed as a system, if it hadn't we wouldn't have captchas or Cloudflare.
In the age of AI we need to better understand where copyright applies to it, and potentially need reform of copyright to align legislation with what the public wants. We need test cases.
The thing I somewhat struggle with is that after 20-30 years of calls for shorter copyright terms, lesser restrictions on content you access publicly, and what you can do with it, we are now in the situation where the arguments are quickly leaning the other way. "We" now want stricter copyright law when it comes to AI, but at the same time shorter copyright duration...
In many ways an ai.txt would be worse than doing nothing as it's a meaningless veneer that would be ignored, but pointed to as the answer.
AI is being used to do copyright laundering, at the same time "we", the people who can't afford to run our own AI, are still subject to absurd rules that AI owners get to ignore, apparently.
The only IP that will be allowed to be stolen is that of other common people.
I would be stealing if I prevented you from making money from it.
Then once smaller competitors are out of business, raise prices.
Of course, force can go into it, such as when a big company sues a smaller company with a frivolous lawsuit that the smaller company can't afford to fight. Then the smaller company goes out of business, and the big company can use their ideas free.