To pay ~~Chiron~~ Charon to ferry them.
AskHistorians
But why did Charon need it? Not like he or she could spend it and he;s or shes friendly with the gods so really can't be hurting for wealth
Who dares question the spending habits of Charon?
He probably needed some sweet DLC for Fortnite or would exchange it for Robux or something.
Charon was a fairy. Styx is an obvious metaphor. Per say phony is the most obvious tell that the underworld is ruled by a Queen. You got to pay to play at the pride party.
First off, the practice was to put the coin in the deceased’s mouth, not on the eyes. And second, it was more widespread than the Greeks, appearing from the ancient near east to early European Christians—so the myth that it was payment for passage over the Styx was probably an attempt to explain a preexisting practice.