Because Ling Ying is a hero, they would rather die in battle than commit suicide in such a cowardly way.

By the way, four or five generations of lancers committed suicide.

Kotomine Kirei is a survivor of the Fourth World War. Although he is not a winner, he is also one of the few insiders who know that the Holy Grail is polluted. Although I haven't finished watching Destiny/Stay Night, I can still infer something from Destiny/Zero of World War IV.

Mainly because the holy grail is polluted by the evil of the world, mostly because the souls of heroes are passively shaken.

For example, Kotomine Kirei was completely distorted by sparks in the Fourth World War, so it is said that his wishes were distorted to the point of destroying the world (eyes drifting).

The way to make the Holy Grail polluted by all the evils in this world is to let the spirit die with regret.

I guessed it myself.

I guessed it myself.

I guessed it myself.

So I'm not sure.