Because he want us as humans to understand when we suffer and face persicutions in that way and when we feel the physical beatings and  emotional stress of rejection we should understand that our lord Jesus Christ also went through all these things. Jesus was human on earth and was here to serve as we are. He lived as a man and died in the same manner a man would in the same position. The pains and suffering of being beaten, rejected, and ridiculed the way He was would be felt today as it was then and when we come across all these things we don't have to ask question because Jesus himself passed through all this