My guesses about OOTS:
1) They really can't get it right musically. Since about 1990, they've been hampered by the fact that Edge hasn't been cloned. They need at least three of him on stage to make all the album noises that sculpt the songs. They're probably reluctant to do another "Staring At the Sun" to it, and make a willowy pseudo-acoustic.
2) It may cut too close to the bone considering the situation with Edge's daughter. Bono seems to thrive to some extent on the nightly catharsis of singing out his demons; Edge may feel differently.
3) Obviously, they have taken the set in a very one-world, political direction. They are not playing up the intimate, personal aspects of the songs, and Original may not fit well with the Africa/human rights push, which basically takes up 2/3 of the show. At this point, I'd expect to hear Crumbs before Original.