Corporal punishment used to be used, and it largely isn't most places. Suspensions filled the void, but apparently those are wrong now. A loss of recess is common at elementary school, but now that's shunned. So what are schools to do? Talking about feelings isn't a solution.

Suspensions can be a deterrent for many kids, who miss out on the social interaction with pers, particularly if they have parents who support schools and believe in disciplining their child when they make mistakes. Too many treat it as a vacation for their kid, or resent it because it inconveniences them.

In general, it incapacitates their ability to do harm. It may not benefit them but it benefits every other kid whose education isn't being hijacked while they are removed. They aren't able to disrupt the learning environment, bully, threaten, fight, or whatever it was that caused the suspension and unsafe action. It's utilitarian. 

Relatively few kids get suspended, and of those who do, most aren't habitual.