Creating memorable printed materials is incredibly important and can achieve a multitude of different objectives. Sales, informational, or some just for fun to create brand awareness.
Getting your brand physically in someone's hand is a hugely powerful marketing tool, whether it be a postcard, one-sheet, shirt, or button. Bringing your brand to life in their home or office creates familiarity and continued support.
Designing for print can be challenging due to the limits of each material, like creating multiple color separations for use in screen-printing or getting your brand across in B&W for easy at-home printing. But these challenges often inform the design and allow a designer to create unique solutions for these physical limitations.