Dr Epstein wrote:

Apart from absorbing the "shock" whether it be from a cast or a hard
hit by a fish, there are some fish that have sharp enough
teeth that fishing without a leader almost always results in your
line being cut.

and also, some fish could cut the line with the dorsal fin. now I
undestand

In sal****er, Bluefish come to mind as requiring
a short wire leader.

there is the same fish in Italy, we call 'serra' and we fish it with
live mullets

--
ciao
Vittorix