It can be rare to only have one question to ask, or one thing to say. In an auditory conversation it can come across as especially ernest, or nervous. What if you could ask your questions, but the questioned only had to answer one, never having known what the other question was? This gives you ambiguity, a chance to express everything but still remain deliberate.
With A or B, the user can send a message with two outcomes - A or B. The receiver can open either message A or message B, but not both.