omissibility - What allows the omission of subject relative pronouns?

“There’s some men wouldn’t look at a girl with a baby.” (Ken
Follett, Fall of Giants)

There is a young student comes here some evenings. (James Joyce,
Dubliners)

“That’s a smell could raise me out of a concrete grave.” (East of

Eden)

“I guess it was Cal asked Lee.” (East of Eden)

I have a friend called me yesterday. (The Syntactic Phenomena of
English)

There are sayings that subject relative pronouns can’t be omitted. But from the examples above on novels and a syntactic book, the construction seems not a rare case or wrong. What allows them the omission?

Answer

All but one of these sentences starts with a phrase saying something exists:

There's …
There is …
That's …
I have a …

I could easily be wrong about this, but my gut feeling is that this is what allows the informal deletion of the subject relative pronoun, although the constructions with it deleted definitely feel informal to me. Taking examples from grammar websites and deleting the subject relative pronoun,
in general I find that the only ones I feel work well are those starting with such an existential construction.

I told you about the woman lives next door.
This is the house had a great Christmas decoration.

The following sentences don't work for me when you drop the "who", although maybe it's just because they're more complicated.

*It took me a while to get used to people (who) eat popcorn during the movie.
*The world is a much sunnier place for people (who) have a positive attitude.