If they don't keep pushing the 1914 or end of days message, what else is left? Then what reason do the average rank and file members have to keep going to the meetings and banging on doors? As an adventist religion it is very important to keep setting dates to keep the rank and file in line. Otherwise the religion (cult) will fall apart.
They don't necessarily need 1914 to set dates, though. 1975 had no basis on 1914 other than that it was "within a generation" of it. It was just the appropriate time for god to act. If they ever need a date, they'll just whip up some numerology and they'll have it. Personally, I think they're trying to emulate the mormons more where it's all about family and emotional appeal, and doctrine is just there to artificially seperate them from "the world." Of course armageddon will always be "soon" but I don't think they want the baggage that the old doctrines bring with them (i.e. easily disproven).
They've dropped the type/antitype nonsense, and that's what 1914 is based on. They seem to be headed in a direction towards easy to grasp doctrine, seperation from "the world," and unquestioning loyalty. The latter will be enforced by constant fear mongering on the soonness of armageddon (the stick). They'll throw in a little emotional appeal and lovey-dovey crap every now and again (the carrot) to keep people happy. Anything beyond that is superfluous.