The primary use of a Raspberry Pi in tech projects is as a versatile, low-cost computing platform for learning, prototyping, and experimentation. Raspberry Pi devices are popular among hobbyists and educators due to their small size, energy efficiency, and support for various programming languages. They can be employed in projects like home automation, robotics, and media centers. The Raspberry Pi community provides extensive resources and tutorials, making it an excellent tool for both beginners and experienced developers to create and experiment with technology.