Agreed with exposure to businesses and domain knowledge and contacts. But I disagree very strongly with the idea that young programmers (college students) can't come up with ideas. Ideas are cheap and plentiful. I have never met a CS student who didn't have at least several ideas bouncing around in their head. And sure, most if not all of those ideas are not billion dollar ideas. Keep in mind that one of the benefits to side projects that the OP mentions is the ability to show employers the projects, in which case the uniqueness matters much less than the actual technical proficiency.