It's good to return things that don't belong to you.
Annie is a student who has borrowed her textbooks from the library all year, and they are due to be returned the same week she'll be on vacation.
Annie wants to avoid going to the library before her vacation.
Annie mails her textbooks to the library.
Annie never returns her textbooks.
The library receives their textbooks and Annie is able to leave for vacation without having to go there.
Annie incurs a late fee, and students who need the textbooks are unable to use them.