I understand that, you're a coach, correct? Do you not use whatever situation you have to better your team and your players?
If we had a live contact scrimmage (which is essentially what preseason football is), then no, I would not put any of my starters in unfavorable situations.
When it comes to actual, meaningful football, I'll give you an example that was probably the best lesson I ever learned coaching:
In 2014, we had one of the strongest teams in the upper state of South Carolina. We had six Division One players on our defense and we were virtually unbeatable on that side of the ball: state leader in interceptions, state leader in sacks, etc.
Our last game of the regular season, we were up 45-0 in the fourth quarter against a two win team. In SC, you used to have an eight quarter rule, so JV players could play up on Fridays for extra depth. We had our JV kids playing by the second quarter...
My boss got pissed at a 14 year old JV running back for fumbling the ball (which led to a scoop and score) and put our backup tailback (and starting OLB) at RB for one play. We ran a simple inside zone play and he picked up a first down, but at the end of the play, a defender fell into his knee and that was that. He was pissed because we lost the shutout in a game that was over before it started.
We lost in the upper state championship (the state semi-final) by two touchdowns to a team we would've beat without that knucklehead's decision.
It's not being competitive. It's not motivational. It's careless. Rex Ryan was emotional all the time and it always got the best of him. Putting Mark Sanchez in with third stringers and training camp bodies was an awful decision. There is no argument.
That is a haunting coaching decision for me. That injury altered his life forever. His recruitment fell off, he ended up at a JUCO in Kansas where he rode the bench, came back home and now I check that local paper every Sunday to see if he's been shot or arrested.
It's very fair to say that Rex Ryan getting Mark Sanchez hurt ruined both of their careers, because it did.