Interrogative

Is "why" now the national standard? What has happened to "how come"? "Because I said so" is the answer to "how come," but nobody seems to be asking "how come" today; it's always "why." This source reports that "how come" is a non-standard variant of why. There used to be a "howcome" domain, but it seems to be gone. Is "how come" a regional usage? The Web isn't helpful.