Sources: Dennis Allen’s recent mishandling of Kendre Miller’s injury created internal frustration, Miller currently healthy but can’t play

People only do what you expect them to do. Warm ups aren't that fun to begin with. How different was a guy like Drew Brees and his pre-practice, pre-game routine. Just like any other job, I know they get paid a lot more, but people need to be told what to do, what is expected of them.
Right, not all people are self-motivated. We as fans expect them to be, but thats just not the way it is. Thats why coaches like Saban had a ton of small rules that put all together becomes the "Saban standard" If all of the players are forced to live up to the standard, then it covers the players that lack self motivation. Just do it, you'll thank me later, kind of deal.