A business card is a physical object that a potential prospect leaves the encounter with. Your brand stays with them. If you meet a prospect and exchange email addresses and phone numbers you each walk away with another contact on your mobile phone -- it ends there. If you hand over a creative business card that makes a great impression that person is likely to show it to other people -- putting you and your brand in front of additional prospects.
When you meet someone that could potentially be a great prospect or connection, do not you want him or her to walk away with a great first impression? A memorable business card does a lot more than just pass on an email address or phone number.
Two individuals with their heads buried in their phones typing away woould not create any kind of significant memory of the encounter. You can easily transfer the information from a business card to your mobile device after the conversation.
A professional business card needs to fit the branding of your business, display your logo prominently, and highlight your website and contact details, so the people you connect with can find you online, on social, or via email.