Don't you think it's nice when villains give their opponents dinner or such before they kill them? I remember how impressed I was as a kid when Mr. Freeze did that for Batman on the old tv show. It's just so civilized. Politeness is definitely a villainous virtue.
Wonder Woman's villains are a pretty polite bunch, I guess because, you know, they're fighting a lady. Take Dr. Poison:
"I am the Princess Maru. My genius will destroy America!"
Dr. Poison, untitled first appearance against Wonder Woman.
Remember, even if you are a cross-dressing Japanese princess and biochemistry genius hell-bent on destroying a freedom-loving democracy and all who would defend it...
it is still polite to introduce oneself.