Spend any amount of time reading the various Mormon themed blogs and you will see any number of reasons people are dissatisfied with and/or have been hurt by the Church and its members. There have been a few attempts to understand the reasons for these things, but mostly there have been unfeeling lists of simple points, trying to codify “why people leave”. To me, aside from the excommunication or removal of those who have shown themselves to be physically or spiritually dangerous to others in the community, coming to Church and being part of the community are mostly a matter of self selection.
People join the Church and attend their meetings because they feel that they have learned the truth of how this life, the next life, and the previous life fit together, want to learn more on how to progress, and want to join with others who have the same goal. There is both power and safety in numbers, and it helps our own growth to work with others with the same goals. Those who fall away do so because the community is no longer a place of peace, but has become, for one reason or another, a place of pain, confusion, or distaste.
This is where self selection comes in. Ultimately, it is that persons choice to stay or go, no matter how deep the dissatisfaction or pain. The question then becomes, what can we do to help them stay, heal, and grow together with us?