Etc is also an abbreviation of et cetera. Only Americans put pointless dots everywhere.

This is all stuff you learn in school. Punctuation isn't obscure or niche. You may not have learnt about semicolons or em dashes in school but you should have and I did. As did anyone that has ever read a novel. There are two semicolons on the first page of the first Harry Potter book, a novel read by approximately every child of my generation. There are loads of examples of the proper use of dashes and other "obscure" punctuation marks in any professionally typeset text.