Cam beat the Dolphins in week 1 and had his team in position to at least tie the Bills. He was competitive against them. Hoyer and Stid would not be. Not only are they indeed worse but there's no point playing them. Neither will be the starter for this team. What would be the value of playing those guys? I don't see it. With Cam you can audition him for next year. You don't audition the other guys, they're probably on the way out the door.
The time to make a change was a few weeks ago, not now when the team's elimination is imminent. Bill didn't, and that speaks loud and clear.