It's a chance for a kid to be part of an organization that's bigger than anything they've ever been a part of.
Take Justin Pierce for example. The former 15 ppg player from William & Mary signed on with UNC and ended up averaging 5 ppg. Do you think he signed there for an opportunity to play big minutes and star for the team? No! It was a chance to finish your career and look back at your time with a much richer basketball experience. Same goes with Jahaad Proctor to Purdue, Jaevin Cumberland to Cincy, Akwasi Yeboah to Rutgers, Max Hazzard to Arizona...
The list goes on. All of these kids were stars from smaller schools: High Point, Oakland, Stony Brook, UC Irvine and took smaller roles to be a chance to play in bigger conferences. You gotta figure these kids knew that PT had to be earned and nothing was promised, so as a coach, you'd love to have an older kid like these in a pinch when you need.