They don't do it because they can't close it down for an involved, and probably lengthy, refurb because attendance would drop too dramatically. Without EE, AK is a very mediocre partial day park. With a yeti-less EE, it's at least got a headline attraction that keeps attendance up enough to keep the guests and cashflow going. With a fully-working EE, I can guarantee you that attendance at AK would be markedly higher, guests would stay longer, more money would be spent, and overall the WDW resort would probably have many people sticking around for an extra day. They clearly took the middle road, and the needed shutdown won't occur until well after Avatar is up and running. Closing it down now would be akin to short-term suicide for the park.