Why does the Bible speak so much about the blood of Jesus?

¹⁰And whatsoever man there be of the house of Israel, or of the strangers that sojourn among you, that eateth any manner of blood; I will even set my face against that soul that eateth blood, and will cut him off from among his people. ¹¹For the life of the flesh is in the blood: and I have given it to you upon the altar to make an atonement for your souls: for it is the blood that maketh an atonement for the soul. ¹²Therefore I said unto the children of Israel, No soul of you shall eat blood, neither shall any stranger that sojourneth among you eat blood. ¹³And whatsoever man there be of the children of Israel, or of the strangers that sojourn among you, which hunteth and catcheth any beast or fowl that may be eaten; he shall even pour out the blood thereof, and cover it with dust. ¹⁴For it is the life of all flesh; the blood of it is for the life thereof: therefore I said unto the children of Israel, Ye shall eat the blood of no manner of flesh: for the life of all flesh is the blood thereof: whosoever eateth it shall be cut off.

¹⁸Whereupon neither the first testament was dedicated without blood. ¹⁹For when Moses had spoken every precept to all the people according to the law, he took the blood of calves and of goats, with water, and scarlet wool, and hyssop, and sprinkled both the book, and all the people, ²⁰Saying, This is the blood of the testament which God hath enjoined unto you. ²¹Moreover he sprinkled with blood both the tabernacle, and all the vessels of the ministry. ²²And almost all things are by the law purged with blood; and without shedding of blood is no remission.

²¹But now the righteousness of God without the law is manifested, being witnessed by the law and the prophets; ²²Even the righteousness of God which is by faith of Jesus Christ unto all and upon all them that believe: for there is no difference: ²³For all have sinned, and come short of the glory of God; ²⁴Being justified freely by his grace through the redemption that is in Christ Jesus: ²⁵Whom God hath set forth to be a propitiation through faith in his blood, to declare his righteousness for the remission of sins that are past, through the forbearance of God; ²⁶To declare, I say, at this time his righteousness: that he might be just, and the justifier of him which believeth in Jesus.

⁵This then is the message which we have heard of him, and declare unto you, that God is light, and in him is no darkness at all. ⁶If we say that we have fellowship with him, and walk in darkness, we lie, and do not the truth: ⁷But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin. ⁸If we say that we have no sin, we deceive ourselves, and the truth is not in us. ⁹If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.