Yes, the vernacular language is essential, because it helps people communicate. The vernacular language is how most people communicate. Language is elastic. It often changes. People should use the language they find most simple to communicate. Language will always develop locally, and the vernacular is important to ease communication between people, most of whom do not have formal educations.
Vernacular language is language that an individual culture creates. In terms of the United States, it is, specifically, words and phrases in individual regions that are different than those used in other regions to describe the same things. Vernacular language is, thus, not essential, it is just a by-product of the differing cultures present within the United States. It is probably always going to exist, but it doesn't need to. If vernacular language did not exist, the United States would still be the United States.