Earlier quoted context omitted.
How else do you tell the bot you do not wish to be scraped? Your analogy is lacking - you didn’t order a package, you never wanted a package, and the postman is taking something, not leaving it, and you’ve explicitly left a sign saying ‘you are not welcome here’.
If you are serving web pages, you are soliciting GET requests, kind of like ordering a package is soliciting a delivery. "Taking" versus "giving" is neither here nor there for this discussion. The question is are you expressing a preference on etiquette versus a hard rule that must be followed. I personally believe robots.txt is the former, and I say that as someone who serves more pages than they scrape
Lets say a large art hosting site realizes how damaging AI training on their data can be - should they respond by adding a paywall before any of their data is visible? If that paywall is added (let's just say $5/mo) can most of the artists currently on their site afford to stay there? Can they afford it if their potential future patrons are limited to just those folks who can pay $5/mo? Would the scraper be able to afford a one time cost of $5 to scrape all of that data?
I think, as much they are a deeply flawed concept, this is a case where EULAs or an assumption of no-access for training unless explicitly granted that's actually enforced through the legal system is required. There are a lot of small businesses and side projects that are dying because of these models and I think that creative outlet has societal value we would benefit from preserving.