1. how come - Adverb
2. how come - Phrase
how come
(idiomatic, informal) Why; why is it; for what reason or purpose; due to what cause?
Synonym: why come
How come you didn’t leave when you had the chance?
If truth is beauty, how come no one has their hair done in the library? Lily Tomlin
If sex is such a natural phenomenon, how come there are so many books on how to do it? Bette Midler
If evolution really works, how come mothers only have two hands? Milton Berle
How come you don't work fourteen hours a day? Your great-great-grandparents did. How come you only work the eight-hour day? Four guys got hanged fighting for the eight-hour day for you. Studs Terkel
I hear you guys all the time talking about Daniel Bryan, trained by Shawn Michaels. One curious thing to me is, how come you guys never mention William Regal? William Regal did the real work with this young man. Shawn Michaels took $3,000 from him, that's all he ever did. Phil Brooks
How come that when I lost my sheep and could not find it, I was questioned; but the hyena who was found with the sheepskin is not questioned. African Proverb