If someone drove their car into a lake, you wouldn't be adding anything to the conversation if you said "The purpose of a car was to drive on the road, not to drive into the lake"

In a similar fashion, you don't really add information to the discussion when you make an analogous statement about the misuse of an AMA thread.

The analogous statement to:

'the purpose of the AMA was to promote the game, not satisfy readers' questions, so they didn't answer questions that would reflect negatively on SimCity V.'

Would be:

'the purpose of the car was to drive on the road, not to drive into the lake, so they chose not to drive into the lake.'