I can't help but wonder why Disney didn't ban selfie sticks in 1985 instead of waiting until 2015. In 1985 WDW had been operating for more than a decade and DL had been operating for 40 years. Surely they should have had a good handle on what should be banned back then.
I guess some people might say that things change over the course of half a century, and that a responsible hospitality company should constantly reassess their policies to guarantee the continued safety and comfort of their guests in light of changing technology, social mores, and vulnerability assessments. But your idea of "if it hasn't been banned by now, it should be allowed forever" has the appeal of the simple bright line.