In Hyperion, the cruciform provides great pain to the one leaving the area of where the Bikuras live(d).
However, in Endymion, during the Pax era, billions of humans on dozens/hundreds of planets are wearing a cruciform.
Why don't they experience intense pain all the time like Duré when he tried to leave the Bikuras ? They are quite far from the Hyperion planet.
The AI Core factions changed their plans between Hyperion and Endymion. Their original plan would appear to have been to keep a large number of humans alive with cruciforms. But nothing more. The cores were using the processing power of their brains but cared nothing for their quality of life. I would have said that the Bikuras were a proof of concept. The cores wanted to confirm that they could keep their victims alive and under control. So the cruciforms used pain to keep them in one place (after all the cores did not want other humans to see them). Critically the cruciforms also made them more and more imbecilic over on-going use. The core was depopulating planets and forcibly giving cruciforms to the humans they took from the planets.
But the core faction of Hyperion lost their battle at the end of the second book.
In Endymion the core has a different plan (I've no idea if it is the same AIs or a different faction - its hard to tell). They still want people to have cruciforms but now they want to use the carrot, not the stick. So they modified the cruciform so it was appealing. They took away the pain, and they took away the mental degradation. But they kept the immortality. As a result the vast majority of the human diaspora was willing to accept the cruciform as a free choice.
Clearly their new plan at no hope of success if it inflicted pain based on someone's location (or indeed if it made people into idiots).
So in short, the AI cores changed their plans.
