Spoken English :Sentences starting with ..How come

1. How come you are so late?'

2. How come he can go but I can't?'

3. How come?

4. How come he didn't get a death sentence?

5. How come you say nothing?

6. How Come These 3 Served More Time?

7. How come you are angry?

8. How come the reporters aren't asking that?

9. How come this song "This Land Is Your Land" became known throughout America.

Question:

It's a line I heard in FRIENDS: "how come you guys have never played poker with us?"

I'd like to know why this sentence is not said like this "how come have you guys never played poker with us?"

If I replace HOW COME with a WHY. Should the sentence be "why you guys have never played poker with us?", or "why have you guys never played poker with us?" ?

Explained here :

If you use "why", it should be "Why have you guys never played poker with us?"

However, "how come ... ?" works like "why is it that ... ?", so the parallel is:

"How come you guys have never played poker with us?"

"Why is it that you guys have never played poker with us?"

How come are you going to India? [ INCORRECT]

“How come you are going to India?” or “Why are you going to India?” [CORRECT]

how come is almost never used where formal writing is demanded, as in academic writing, but is frequently used where informality is okay, as in fiction dialogue and speech:

           TOTAL    SPOKEN  FICTION  MAGAZINE  NEWSPAPER   ACADEMIC
HOW COME   2689     882     1318     283       164         42  

In American English, at least, how come? is informal, but probably not considered slang.

"How come?" is simply a shortening of "How does it come to be (that)?".

is using how come in the example conversational slang?

Yes, it is part of spoken speech, but very rarely in written speech.

And also, is "How come you are angry?" proper english?

No, "how come" is not proper English. It's colloquial, or informal. The actual phrase is "how came", as in:

How came you to be so angry?

Although it is not improper, to use "how come" it in the place of "why" is an American idiom that some teachers would like to eliminate. It is most often used today in informal speech, even though it appears in educated journals in the 19th century. It is a shortened version of the phrase, "how does it come to be..."

"How come" is believed to be short for "how did it come about that," "how is it that," or "how comes it."