#5 Tracking results is simple
While it may be difficult to interpret insights from Facebook or Twitter and translate that into real dollar amounts, it's easy to track the results of an email campaign. You can see who opened an email, who clicked a link inside of it, and whether they completed an action, like a sale or other conversion. Being able to measure results quickly means you can adapt your next campaign and maximize your sales.
#4 Email is Required
An email address might as well be a social security number these days. In 2013, the number of worldwide email accounts is predicted to grow to 3.6 billion. That's about half of the population of the entire world. Everything from job applications to your taxes have fields for an email address. Email is universal and in the modern world it's a requirement.
When you're creating a voice for your brand on social media outlets, it's important that you keep that tone consistent across your email campaigns. If you keep email separate from your social campaigns, then you risk confusing your target audience and losing some of the hard-earned value you've already built for your brand.
#2 Targeted Messages
Let's say you wanted to have a different voice for different parts of your brand's target audience. You can't split your twitter followers in half and tweet different messages to each group, but you certainly can with email. As a direct marketing channel, email allows you to split your audience into separate lists and send targeted messages to various groups based on past behavior, interests, locations, or any other criteria that might help you reach your niche.
#1 Return on Investment
Despite social media's exponential growth in the past few years, Email consistently outperforms Twitter and Facebook. If that's not enough to convince you: every $1 dollar spent on email marketing in 2012 created about $40 in revenue.