Here is an interesting article about why some don’t or can’t StayLDS. It is found at the blog Zelph on the Shelf The author puts forth the idea that people do not stay LDS for too little interest, and for too much interest. This quote sums it up.
We can observe that church membership yields the greatest fulfillment to people of mild interest — the ones who derive a sense purpose and community from it, but who aren’t as interested in its history or doctrine. It works best for those who like the scriptures and the prophets but who aren’t interested enough to examine their accuracy or ethics. It works best for those who like the idea of paradise, but who aren’t as interested in the logistics of creating one now.