I think the "cult personality" appeals to some people for a lot of reasons.
They can operate from a perceived position of authority - they know their bibles, goddammit, and nobody else compares to them in that regard. (I know they don't actually "know" the bible from a scholarly or learnèd perspective, but they believe they do, because the WTS tells them they do.)
They can follow rules / Principles™ that require no ethical or moral quandary on their part. All the thinking has been done for them. Or so they've been told. This, they believe, absolves them of any responsibility should someone protest against inhumane practices like shunning or child sacrifice. They believe they are doing these things for a greater cause, one that only they can appreciate and understand. If you don't get it, it's because you're not Privileged™ like they are.
There is a certain moral and ethical laziness involved in being a JW. If all you need to do is look up answers in the Publications™ for any question you might have under the sun, you are depriving yourself of moral and ethical growth. You are depriving yourself of the opportunity to examine all the various possible outcomes and come to your own conclusions about what is the most beneficial to the most people involved, or the least harmful outcome, or the most fair, or most reasonable conclusion to reach. The person's conscience becomes dependent on dogma to the point that no thought or careful consideration is required for any decision that they need to make. Often their own consciences become stunted by and strangled in WTS legalism, rather than being allowed to grow and operate freely, according to truth, love, mercy and justice.