Broyles recently missed some time in practice, so clearly the Lions don't want to rush him back into game action. He's made great progress from his latest torn ACL, but there's no sense in hurrying him back for a preseason game. The same goes for Harris, who was just activated from the PUP list last week.
The other players on the list have missed varying amounts of practice time as well since the start of training camp. Delmas is probably the most notable name on the list, and he said earlier this week that he was hoping to play. The Lions have been extra careful with his practice reps, so it's no shocker he's sitting this one out.