You kind of answer your own question by saying there are only so many minutes available. The goal is to win games, to do that you have to put your best players out there for as many minutes as they can reasonably handle and be effective.
He is doing fine as a freshman. Shooting 34% on 3's. Will likely and hopefully get better on that in subsequent years. Getting off a clean look at a 3 in Iowa high school basketball is much different than a Big 10 game. Other things he does well is protect the ball (turnover rate very low), make free throws (11-12). But he's a pretty poor rebounder. Gets only 7% of the opponent misses when he's on the floor. His DR% is lower than Toussaint and significantly lower than PMac, CMac and Ulis (note, it is better than Bohannon). He is almost exactly the player I thought he would be as a freshman, given his skill set and background. I wouldn't be shocked if he turned around a game at some point by coming in and hitting a couple of 3's to give Iowa some juice. He did pretty much that against Western Illinois. Iowa probably was not going to lose that game, but he got them out of a funk by hitting some shots in a hurry.
He will get better as he gets used to the speed of the college game and understanding where and how he can get his shot off, as well as the type of effort it will take on the defensive end. But for this year, if he were to play more it means others have to play less. Neither Murray should be losing PT so Sandfordt can get more. Perkins, Ulis and Toussaint probably need more minutes, not less. Only realistic way of it happening is if Bohannon or the McCaffery brothers play less. And that is unlikely to happen. If someone were to get injured among any of the perimeter players, he probably gets more minutes. But barring that, more time is there next year with Bohannon and CMac's departures.