marketing and sales

There is often a divide between Marketing and Sales. Both departments have the primary focus to generate revenue for the company. However, the primary goals of marketing are to look at the big picture, promote the company, product or service, and brand and generate leads for the sales team. For sales, the goals are to leverage the brand and tools and hit sales volume goals by executing on the leads generated by marketing. So, with similar but different purposes, why are companies always looking for a VP of Sales and Marketing?