When you send an email, the real advertisement is the subject line.
Think about it. If only 15% of your customers open an email you send, that means 85% only ever see the subject line.
With social media and digital advertising on the other hand, 100% of customers get the whole picture. Even if they just scan, your branding sinks in.
And what's more, pictures (and video) are a lot more powerful than text when it comes to influencing customer behavior.