My emails with my little brother reminded me how almost no one in my family or ward has asked why I've left the church. I think that there are several things going on.
What his email reveals is how Mormons have been taught to think of apostates as misguided sinners who have lost the Spirit and fallen away from or rejected the truth. The stated reasons for their apostasy don't really matter because the prophets and scriptures have pretty clearly stated why people apostatize. Everything else is just rationalizations. These people don't ask because they think they already know the answer.
I think another reason is that they don't want to know the answer. If the reasons were strong enough to break my testimony then maybe it's better not to know.
Finally, the last reason I've observed are those members who are aware of the issues and still remain active in the church. This was really surprising to me. I learned things such as the nature of Joseph Smith's polygamy that I simply couldn't swallow. Those people have somehow made peace with the uncomfortable facts. Some put the issues on a shelf or reformulate their beliefs to accommodate the facts while others no longer believe but continue to remain active and pretend to believe in order to keep the peace and reap the benefits of membership. That last group was especially surprising to me. These people don't ask because they already know what the problems are.