I suspect many people wonder about this—but God never does anything by accident, and He had a purpose in giving those sacrifices to His people in the Old Testament.
His purpose was to teach them some important truths—truths they needed to understand so they could serve Him. They also needed to know those truths so that they would be prepared for the time when God would send His Son into the world. The Bible says the Old Testament Law was like a teacher or schoolmaster, "put in charge to lead us to Christ" (Galatians 3:24).
What was God teaching them through those sacrifices? For one thing, He was teaching them the seriousness of sin. Sin isn't insignificant or easily excused; blood must be shed to atone for it. God also was teaching them that He is holy and pure, and sin must be judged. But God was also teaching them about His grace and mercy, because instead of being put to death for their own sins, He was willing to accept a substitute.
But those sacrifices are no longer needed, because by His death on the cross Jesus made the final sacrifice for sin! The Bible says, "But now he has appeared once for all... to do away with sin by the sacrifice of himself" (Hebrews 9:26). Are you trusting Him for your salvation?