We care because we believe that every word and phrase of Scripture is inspired and we know not a word or phrase is mere filler. Therefore we also know there must be a reason the story of Abraham and Isaac continues with the sacrifice of the ram as a burnt offering. We know there is a reason the story does not end at verse 12 with the vindication of Abraham's faith and God's love. There must be a sacrifice to make both Abraham and Isaac right with God. Because of sin none of us are right with God.
Sin is serious business.
If anything matters, sin matters. It matters deeply and profoundly. Sin is so serious that it demands a sacrifice. Many people today do not take sin seriously. Many people today do not realize the terribleness of sin.