If Anubis blocked crawler requests but helpfully redirected to a giant tar ball of every site using their service (with deltas or something to reduce bandwidth) I bet nobody would bother actually spending the time to automate cracking it since it’s basically negative value. You could even make it a torrent so most of the be costs are paid by random large labs/universities.
I think the real reason most are so obsessed with blocking crawlers is they want “their cut”… an imagined huge check from OpenAI for their fan fiction/technical reports/whatever.