just because no one else signed Sheets doesn't mean that he doesn't have skills or potential. Maybe he isn't ready for prime-time but we should still be excited about a player with his skill set and what he can add to our team. We don't have home-run threats and Sheets is potentially one of those.
I think teams generally like to put players they know on their practice squad, players they worked with all summer. We shouldn't take Sheets being on our PS as a condemnation of him, but merely as the fact that we have a good looking player with interesting potential ready to contribute in the future.