Is it really necessary to add schema?

[davidsmith21]

Not necessary but it's important in the age of Hummingbird and RankBrain.
Schema markup, found at Schema.org, is a form of microdata. Once added to a webpage, schema markup creates an enhanced description (commonly known as a rich snippet), which appears in search results.

Schema markup is especially important in the age of Hummingbird and RankBrain. How a search engine interprets the context of a query will determine the quality of a search result. The schema can provide context to an otherwise ambiguous webpage.