A telephone call might start like this
Alice: Hello, who is this?
Bob: Hey, Bob here. Is this Alice?
Alice: Yes, indeed.
Now in school I learned to use this for objects in my close range and that for objects further away.
Is there a reason why we use "who is this" instead of "who are you"? I realize it sounds more polite this way, but can't help to feel grammatically awkward.