If by "preserve," you mean should w

If by "preserve," you mean should we make sure people keep speaking those languages, no. I think it is perfectly natural for languages to change, evolved, and become dead, and we shouldn't try to stop that. But if by "preserve," you mean should we preserve a knowledge of the languages, then yes. History depends on our ability to translate dead languages. Cracking Egyptian hieroglyphics has helped us to understand a lot about ancient Egypt than we didn't know before. Deciphering the Mayan written language helped historians, too