I also _understand_ why they exist. It's simple: It makes code marginally easier to write.
But writing confusing, unintuitive and honestly plain ugly code. Just so you can save a second after clicking run and the compiler tells you the mistake is a bad reason.
I've done plenty of SQL, and I've regularly run in to the "fuck about with fucking trailing commas until it's valid syntax"-problem. It's a very reasonable convention to have.
What should really happen is that the SQL standard should allow trailing commas:
select
a,
b,
from t;Yes. Typically shared sense of "readability" in a community for language X translates to "idiomatic patterns when writing X". There's no real thing as readability in a universal sense. It's a placeholder statement for "it's easier for ME to understand", double emphasis on "ME". Within a community, "readability" standards are merely channeling the idiomatic patterns within that community as for most members they'll be easier for the person to understand as it's what they're used to seeing.