In a class room setting, why do people look at you when you are asking a question? Picture this scenario:


You are a student enrolled in a large class
You arrived slightly late to the class, so you are sitting at the back of the class
You raise your hands to ask the teacher a question. 
As you speak, you observe that the entire class turn their body sideways to look at you, even the students who are sitting in the front row. You feel self-conscious



Three thoughts are now going through your mind:


What are "ears" for, again?
It must be really uncomfortable and awkward to twist your body like that.
What is the incurred "loss" if the other students did not look at you and simply listened?


Can some expert chime in the reasoning as to why students have to look at you when they are listening?

Could this be some sort of form of peer pressure?

Could the act of looking help to localize the sound (or synthesize the information) in some way? 

Do we look so we can prejudge? For example, if we see that the asker/speaker is another professor, we pay more attention to the question as it might be more sophisticated than asked by a student.
Well, your ears are shaped in a way that is optimized for sound sources in front of you, so it could be that. But my non-expert bet is that probably they're using gaze to signal that they're paying attention. The signal is not just to you "I'm following what you're saying" but to everyone else as well, "hey, check out what's going on over there" creating joint attention that coordinates the group in thinking about your question. This might be uncomfortable for you (although it's probably a compliment that you're worth paying attention to), but the general mechanism of having super-obvious cues to attention and a predisposition to follow them to create joint attention is a very effective way of coordinating social behavior. This is so fundamentally human that most people take it for granted, but that doesn't stop academics from studying it. You could maybe try something like 

Pfeiffer, U. J., Vogeley, K., &amp; Schilbach, L. (2013). From gaze cueing to dual eye-tracking: novel approaches to investigate the neural correlates of gaze in social interaction. Neuroscience &amp; Biobehavioral Reviews, 37(10), 2516-2528. 

or

Brooks, A. M. M. R. (2017). Eyes wide shut: The importance of eyes in infant gaze-following and understanding other minds. In Gaze-Following (pp. 229-254). Psychology Press. 

...if you really want a deep-dive into this.