> "Why do you sing when you talk? It's rude and annoying. Speak like a human, please."

What could be ruder than a question like that?

More people should sing when they talk. It might make their conversation more interesting.

More info - though awkwardly presented:

http://en.wikipedia.org/wiki/High_rising_terminal

I never heard "uptalk" while growing up in the U.S. Northeast. By the early '70s (before "Valspeak") it was endemic in parts of the South, perhaps especially, as Wikipedia says, among high-school and college women.

My own guess is that the interrogative rising pitch substitutes for an unspoken question like "Do you follow me?" "Is that correct?" or the dreaded and therefore suppressed, "Ya know?"