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.
Gone are the days when people carried their business cards with them so that they could give these small paper business cards to colleagues and business associates. The small paper business cards where often made of high quality paper that included business and contact information of the person. Nowadays people are opting to create virtual business cards that are online business cards that can be directly sent to associates directly online.
Everything we do in business today is digital -- sending mail, signing contracts, attending meetings, even networking. The business card is one thing that digital will not fully replace anytime soon.
If you met two individuals and one was scrambling to find a pen and something to write on and the other person simply pulled out a business card, who would you want to do business with? Showing that you are prepared at all times is a great indicator that you are professional.