Email marketing may not be as sexy as social media and viral marketing, but it's a lot more personal and as a result, remains one of the most effective means of marketing.
To put that into context, whilst businesses spend on average just 10% of their digital marketing budget on email marketing, an email will generate 25x more clicks than social media.
Very simply, you know more about your audience. You can personalise an email; not merely addressing it to them, but including content that is relevant to their interests. You can run split tests to identify what they respond to and what day and time they prefer to read their emails. Email marketing is the most targeted type of marketing you can undertake.