Imprisonment is the most perverse punishment ever thought up by humans. A person actually interested in justice would never employ this.
To maximize convincing power for people that don't share my axiology, I'll give the pragmatic reasons first. One is that imprisonment stops the criminal from working, which means they can't support themselves and taxpayers are forced to feed them. For fuck's sake whose idea was it to punish criminals by forcing them to continue being a drag on their victims. (It's important that the taxpayer's anger here should be directed at the government, not the criminals, who didn't choose to cause this situation and aren't the ones with the power to stop it.)
Then there's the reason of increased collateral damage: imprisonment also severely harms the criminal's friends and family, as well as whatever employer, customers, or coworkers they might have. Most other forms of punishment don't lead to as much suffering for those around the criminal.
Now for the spiritual reason. Compare it to the simple method of beating the criminal up, and think about the effect your punishment has on the criminal in each case. No one likes pain, but what does a penitent criminal fear that a shameless one does not? Being denied the chance to make amends. And as explained above, that is exactly what imprisonment does. You aren't allowed to work your job and give the proceeds to your victim. You have to stay in a cell and continue to live off your victim's resources. That means the more an imprisoned criminal repents, the more they suffer. What a fucked up system.