...Why?
It works for a variety of reasons...
It allows targeting
It is data driven
It drives direct sales
It builds relationships, loyalty and trust
It supports sales through other channels
Modern email marketing services and solutions support database integration, segmentation and various other tricks and techniques for improving the targeting of outgoing messages. Advanced methods generate on-the-fly emails customized down to an individual recipient basis.
And every email campaign you send out generates a heap of actionable data you can use to refine your approach and messages.
Email promotions and offers generate immediate action: sales, downloads, inquiries, registrations, etc. Informative email newsletters and other emails send people to offline stores and events, prepare the way for catalogs, build awareness, contribute to branding, strengthen relationships, encourage trust and cement loyalty.