My theory is that snippet and reply may lead to taking quotes out of context and replying with an uncharitable interpretation of the snippet.
So while top posting may be less logical and efficient, I believe it may be more conducive to a friendly discussion.
Of course I could be completely mistaken about this, and it was just a coincidence that the communities I was involved in where top posting was heavily criticized had cranky people in them who would have found something to get upset about regardless of posting style.
Edit: I don't mean to imply that you are one of those cranky people just because you like bottom posting or snippet and reply! :-) Just observing something I noticed in online forums many years ago.