Athletes don't get their stipends in the summer. They also can't spend time with the official trainers/coaches on campus so most ARE working out with guys like Jordan Pendelton off campus.
Some guys are working as Security Guards or at the BYU Youth Camps to try and put food on their plates. They can't go out and get real jobs.
It's easier to go home and have mommy cook your food for free. There is a place around me (Laione Built Fitness) that had players from Michigan St., BYU and UCLA working out this past month.
Unless Bronco paid his guys under the table... his best option was for them to go home.