Suicide is the leading cause of death among young men because a combination of medical science and safety regulations have made all the other causes incredibly unlikely.

Why is it not the leading cause of death for young women then?

Because something else kills more of them.

I don't see how this kind of truism helps the discussion.

Honestly, looking at the ONS data I grabbed, it's not even a truism. Male suicide is the top (non-accidental, which isn't mentioned in the article) cause of death among all people aged 15-45 in England and Wales. Boys and Men in that age category just do twice as much dying overall, and the only significant categories (of my arbitrary cutoff) that women are doing worse in is cancer and childbirth.

Oh I was specifically talking about onion2k's statement that essentially boiled down to "X is not the leading cause of death for young women because something else is", which is a truism and not useful in any way.

The interesting information here would be why it is for one cohort but not the other.