Alexei ...
This is the whole point here ... the Sacrifice was NECESSARY, for OUR behalf.
He had to take the Penalty so that WE could go FREE and so that the means of Forgiveness of our sins, depends on his sacrifice and Holy work finished on the cross, and not our so called good works.
God said in Hebrews 9:22 - "and without shedding of blood is NO remission."
Jesus had to be sacrificed for our sins, he HAD to pay the penalty, for our sins, the JUST was PUNISHED for the UNJUST. I hope you understand my point.
Thanks.