How come I can't buy a toilet that reports how much water it has used today, this month, this year? (The New York Times)
Is "how come" really very informal English?
I ask because the book I'm reading says that it is, but, strangely, I found many occurrences of "how come" in English newspapers.
However, if that book is wrong, can anybody explain whether "how come" is more proper of "why" in some contexts rather than in others?