Certainly you need to if you wish to showcase your business or service at google results. Schema.org is a joint effort between Google, Microsoft and Yahoo! and is now the highly recommended way to describe elements on the web. For e.g. If your site is about recipe and you have implemented schema, Google will display your results in rich snippet format which will attract the searchers resulting in more clicks and conversions. On the other hand, if schema is not implemented your website will be displayed along with the regular results which fail to catch the eye of the potential visitor.